[feature/editor-code-tabs] Allow tabs when typing code

Allow tabs when typing code in textarea
Keep indentation when typing code in textarea

PHPBB3-11557
[feature/editor-code-tabs] Correctly calculate end tag location

PHPBB3-11557
[feature/editor-code-tabs] Adjust code style to match guidelines

PHPBB3-11557
Merge remote-tracking branch 'remotes/cyberalien/feature/editor-code-tabs' into develop

# By Vjacheslav Trushkin
# Via Vjacheslav Trushkin
* remotes/cyberalien/feature/editor-code-tabs:
  [feature/editor-code-tabs] Adjust code style to match guidelines
  [feature/editor-code-tabs] Correctly calculate end tag location
  [feature/editor-code-tabs] Allow tabs when typing code