This commit fixes a bug where, if a note contained uppercase characters
(for example `Note.md`) but was referred to using lowercase
`(`[[note]]`), that note would not be found.
Previously, links referencing a heading (`[[note#heading]]`) would just
link to the file name without including an anchor in the link target.
Now, such references will include an appropriate `#anchor` attribute.
Note that neither the original Markdown specification, nor the more
recent CommonMark standard, specify how anchors should be constructed
for a given heading.
There are also some differences between the various Markdown rendering
implementations.
Obsidian-export uses the [slug] crate to generate anchors which should
be compatible with most implementations, however your mileage may vary.
(For example, GitHub may leave a trailing `-` on anchors when headings
end with a smiley. The slug library, and thus obsidian-export, will
avoid such dangling dashes).
[slug]: https://crates.io/crates/slug
