Fix debian packages (copyright needed)

assets/linux/copyright

@@ -0,0 +1,4 @@
+This package was created by the Betaflight open source flight controller firmware project (https://github.com/betaflight/betaflight).
+
+All of the code is covered under the terms of the GPL version 3. See the
+file /usr/share/common-licenses/GPL-3 for more information.

gulpfile.js

@@ -506,6 +506,7 @@ function release_deb(arch) {
              changelog: [],
              _target: 'opt/betaflight/betaflight-configurator',
              _out: RELEASE_DIR,
+             _copyright: 'assets/linux/copyright',
              _clean: true
     }));
 }

package.json

@@ -26,7 +26,7 @@
     "del": "^3.0.0",
     "gulp": "~4.0.0",
     "gulp-concat": "~2.6.1",
-    "gulp-debian": "~0.1.7",
+    "gulp-debian": "~0.1.8",
     "gulp-install": "^1.1.0",
     "gulp-rename": "~1.2.2",
     "gulp-zip": "^4.1.0",