.editorconfig: Add file to speed up editor configuration

VS2017 supports this natively.
VS2015 and earlier can use this with the editorconfig extension.
Most other popular IDEs support this natively or via a plug-in.

For more details please visit: http://editorconfig.org/

.editorconfig

@@ -0,0 +1,19 @@
+# EditorConfig is awesome: http://EditorConfig.org
+# Since OBS follows the Linux kernel coding style I have started this file to
+# help with automatically setting various text editors to those requirements.
+
+# top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file.
+[*]
+insert_final_newline = true
+trim_trailing_whitespace = true
+charset = utf-8
+indent_style = tab
+indent_size = 8
+
+# As per notr1ch, for 3rd party code that's a part of obs-outputs.
+[plugins/obs-outputs/librtmp/*.{cpp,c,h}]
+indent_style = space
+indent_size = 4