Add support for region folding

[CharNikita]

Currently, custom folding regions (#region / #endregion, <editor-fold> / </editor-fold>) do not work in HOCON files.
The IDE ignores these markers, even though standard folding for objects and arrays works correctly.

Expected behavior:

• Comments like #region name and #endregion (and <editor-fold> / </editor-fold>) should be recognized as foldable regions by implementing CustomFoldingBuilder.

This would make it possible to use familiar region folding in large configuration files, improving readability and navigation.