Bug 24774: Set JSON indentation of 2 spaces in .editorconfig

To test:
1. Start an editor that supports .editorconfig
2. Open or create a JSON file
3. Observe identation is set to 2 spaces by default

Sponsored-by: Hypernova Oy
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

.editorconfig

@@ -10,3 +10,6 @@ indent_style = space
 indent_size = 4
 # New files charset should be UTF-8
 charset = utf-8
+
+[*.json]
+indent_size = 2