Outliner mode bugs / enhancements

[gbro3n]

• Image hover / preview not working on indented blocks.
• We need a means of viewing everything under / related a [[wikilink]] in a single view - in addition to backlink mentions
• Research value of stable or hashed IDs for outliner blocks

[gbro3n]

• Fenced code block completion buggy under outliner blocks
• Format on save is interfering with indent structure (duplicating before reverting indentation)
• Cursor / indent positioning, child indent behaviours

The above are completed.