Feature request: Add option to use level 1 headings for node labels

[langmerah]

Some knowledge management systems (like Zettelkastens) append a unique identifier (like timestamps) to the beginning of note titles to make organisation easier. However, this makes viewing the graph cluttered when trying to get the gist of a web of connections from the titles alone. These systems also often have notes with YAML front matter or level 1 headings without the identifier, which could be used as node labels to produce a more "readable" graph.