Currently the implementation is very limited.
Ref: #24
- Outline must be open and have been loaded for it to work (requires
lazy loading or headless loading of Sidebar)
- Empty string returned if cursor is not in any symbol ('closest' symbol
not yet supported)
- Line column not used
- Returning concatenated symbol names rather than a list of tables with
node info (requires a refactor of outline.SymbolNode type)
- Subject to config.symbols.filter and folds (requires finding hover
list somewhere outside of writer.make_outline)
