Add contributing document

.github/CONTRIBUTING

+## Contributing to nheko
+
+Any kind of contribution to the project is greatly appreciated.
+
+- Bug fixes
+- Implementing new features
+- UI/UX improvements/suggestions
+- Code refactoring
+- Translations
+
+### Working on new features
+
+Everything on the issue tracker is up for grabs unless someone else is 
+currently working on it. 
+
+If you're planning to work on a new feature leave a message on the Matrix room 
+(or in the corresponding issue), so we won't end up having duplicate work.
+
+### Submitting a translation
+
+Example for a Japanese translation.
+- Create a new translation file using the prototype in English
+  - e.g `cp resources/langs/nheko_en.ts resources/langs/nheko_jp.ts`
+- Open the new translation file and change the line regarding the locale to reflect the current language.
+  - e.g `<TS version="2.1" language="en">` => `<TS version="2.1" language="jp">`
+- Run `make update-translations` to update the translation files with any missing text.
+- Fill out the translation file (Qt Linguist can make things easier).
+- Submit a PR!
+
+
+### Code style
+
+We use clang-format to enforce a certain style as defined by the `.clang-format`
+file in the root of the repo. Travis-CI will run the linter (macOS job) on each 
+commit and the build will fail if the style guide isn't followed. You can run the
+linter locally with `make lint`.
+
+
+If you have any questions don't hesitate to reach out to us on #nheko:matrix.org.

README.md

@@ -163,8 +163,7 @@ You can also install nheko by running `nix-env -f . -i`
 
 ### Contributing
 
-Any kind of contribution to the project is greatly appreciated. You are also
-encouraged to open feature request issues.
+See [CONTRIBUTING](.github/CONTRIBUTING)
 
 ### Screens