etc changes related to code-style docs

* Add a "Code Style" section in CONTRIBUTING
* Move .clang-format to etc/
* Add a short comment on clang-format and editorconfig file

.editorconfig

@@ -1,4 +1,6 @@
 # EditorConfig
+# See this if your editor doesn't have built-in editorconfig support:
+# https://editorconfig.org/#download
 
 # apply to all files
 [*]

etc/.clang-format

@@ -1,3 +1,6 @@
+# clang-format doesn't dictate the project's code style and can mess up a
+# couple edge cases. However it comes quite close and can be used for fixing
+# most style issues automatically on new changes via `git-clang-format`.
 ---
 
 Standard: c++03

etc/CONTRIBUTING.md

@@ -23,7 +23,7 @@ Contribution Guideline
 When contributing, make sure:
 
   * Your contribution falls under nsxiv's scope and aim
-  * You follow the existing code style (see [.editorconfig](../.editorconfig))
+  * You follow the existing code style (see the "Code Style" section below)
   * You open the pull request from a new branch, not from master
   * To avoid using force pushes, especially for bigger patches. Only use them
     when there's merge conflicts.
@@ -44,6 +44,21 @@ to work on. You can also filter the issues via label:
   (Intermediate/Experienced) Issues where we require some help.
 
 
+Code Style
+----------
+
+`nsxiv` mostly follows the [suckless code-style][sl], with a few exceptions.
+If your editor supports [.editorconfig](../.editorconfig) then you'll already be
+off to a good start without needing much manual intervention. Additionally we
+provide a [clang-format](./.clang-format) configuration for reference, which you
+may use via [`git-clang-format`][cf] to format the changes you've made (please
+do not run it globally on the entire code-base since clang-format gets a decent
+amount of edge cases wrong).
+
+[sl]: https://suckless.org/coding_style/
+[cf]: https://clang.llvm.org/docs/ClangFormat.html#git-integration
+
+
 Development workflow for maintainers
 ------------------------------------