editorconfig: only apply to .c and .h files (#433)

otherwise, it ends up applying to the manpage and git commit messages
too.

Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/433
Reviewed-by: eylles <eylles@noreply.codeberg.org>
Reviewed-by: explosion-mental <explosion-mental@noreply.codeberg.org>

.editorconfig

@@ -2,8 +2,8 @@
 # See this if your editor doesn't have built-in editorconfig support:
 # https://editorconfig.org/#download
 
-# apply to all files
-[*]
+# apply to all .c and .h files
+[*.{c,h}]
 
 # top-most EditorConfig file
 root = true