[ticket/12951] Added editorconfig

PHPBB3-12951
[ticket/12951] Made editorconfig file comments better

PHPBB3-12951
Merge pull request #2853 from callumacrae/ticket/12951

[ticket/12951] Added editorconfig
Merge branch 'develop-ascraeus' into develop

# By Callum Macrae
# Via Callum Macrae (1) and Dhruv Goel (1)
* develop-ascraeus:
  [ticket/12951] Made editorconfig file comments better
  [ticket/12951] Added editorconfig