Update .editorconfig

Update .editorconfig to indent yml files with 2 spaces instead of 4.
This was already the case for some of the workflows & hopefully this'll
promote a bit more consistency in future changes.

.editorconfig

@@ -7,3 +7,6 @@ indent_size = 4
 end_of_line = lf
 insert_final_newline = true
 trim_trailing_whitespace = true
+
+[{*.yml,*.yaml}]
+indent_size = 2