Documentation: Add code of conduct

Communities have standards regarding behaviours they consider acceptable
or not acceptable, and expect community members to follow those
standards. libcamera is no different, even if it has never clearly
expressed those standards in a formal code of conduct document.

Like software licenses, codes of conduct can be written in a myriad of
ways. And like software licenses, using a widely adopted code of conduct
instead of writing our own can help bringing clarity. One such standard
code of conduct is the Contributor Covenant, stewarded by the
Organization for Ethical Source.

The Contributor Covenant has been adopted by the freedesktop.org
organization, which hosts a large number of projects historically
related to graphics, and more recently to multimedia in general.
freedesktop.org offers services such as git hosting with CI, which
libcamera could benefit from. There is therefore a clear incentive to
choose the same code of conduct as freedesktop.org, and no known
drawback.

As a first step towards this, and to keep the libcamera code of conduct
history clear in git, copy the original Contributor Covenant v1.4 from
https://github.com/EthicalSource/contributor_covenant/. "v1.4" is
ambiguous as the document initially published as v1.4 has received small
(but sometimes significant) modifications over time. The version
imported here ([1]) is the most recent "v1.4", from tags/2.1 (commit
8a3be1350b07 "Merge pull request #979 from JustArchi/patch-2").

[1] https://github.com/EthicalSource/contributor_covenant/blob/2.1/content/version/1/4/code-of-conduct.md

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

Documentation/code_of_conduct.md

@@ -0,0 +1,78 @@
+
+# Contributor Covenant Code of Conduct
+
+## Our Pledge
+
+In the interest of fostering an open and welcoming environment, we as
+contributors and maintainers pledge to make participation in our project and
+our community a harassment-free experience for everyone, regardless of age, body
+size, disability, ethnicity, sex characteristics, gender identity and expression,
+level of experience, education, socio-economic status, nationality, personal
+appearance, race, religion, or sexual identity and orientation.
+
+## Our Standards
+
+Examples of behavior that contributes to creating a positive environment
+include:
+
+* Using welcoming and inclusive language
+* Being respectful of differing viewpoints and experiences
+* Gracefully accepting constructive criticism
+* Focusing on what is best for the community
+* Showing empathy towards other community members
+
+Examples of unacceptable behavior by participants include:
+
+* The use of sexualized language or imagery and unwelcome sexual attention or
+  advances
+* Trolling, insulting/derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or electronic
+  address, without explicit permission
+* Other conduct which could reasonably be considered inappropriate in a
+  professional setting
+
+## Our Responsibilities
+
+Project maintainers are responsible for clarifying the standards of acceptable
+behavior and are expected to take appropriate and fair corrective action in
+response to any instances of unacceptable behavior.
+
+Project maintainers have the right and responsibility to remove, edit, or
+reject comments, commits, code, wiki edits, issues, and other contributions
+that are not aligned to this Code of Conduct, or to ban temporarily or
+permanently any contributor for other behaviors that they deem inappropriate,
+threatening, offensive, or harmful.
+
+## Scope
+
+This Code of Conduct applies within all project spaces, and it also applies when
+an individual is representing the project or its community in public spaces.
+Examples of representing a project or community include using an official
+project e-mail address, posting via an official social media account, or acting
+as an appointed representative at an online or offline event. Representation of
+a project may be further defined and clarified by project maintainers.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported by contacting the project team at [INSERT EMAIL ADDRESS]. All
+complaints will be reviewed and investigated and will result in a response that
+is deemed necessary and appropriate to the circumstances. The project team is
+obligated to maintain confidentiality with regard to the reporter of an incident.
+Further details of specific enforcement policies may be posted separately.
+
+Project maintainers who do not follow or enforce the Code of Conduct in good
+faith may face temporary or permanent repercussions as determined by other
+members of the project's leadership.
+
+## Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4,
+available at https://www.contributor-covenant.org/version/1/4/code-of-conduct.html
+
+[homepage]: https://www.contributor-covenant.org
+
+For answers to common questions about this code of conduct, see
+https://www.contributor-covenant.org/faq
+