Source and docstring info for Java classes and members. Requires JDK11+.

Leaves `:doc` untouched.

Adds `:doc-fragments`, `:doc-first-sentence-fragments`, and `:doc-block-tags-fragments` attributes.
These represent sequences of 'fragments', which can be of text or html type:

* `:doc-fragments` represents the body of the comment, including the first sentence and excluding any block tags
* `:doc-first-sentence-fragments` represents the first sentence of the doc comment.
* `:doc-block-tags-fragments` represent the 'param', 'returns' and 'throws' documentation.

Clients are expected them to render the html fragments using a client-specific method,
and then join the client-processed strings into a single string.

Fragments of "html" type may have leading/trailing whitespace, which is to be ignored
(since an HTML parser would ignored it anyway).

Fragments of "text" type have significant, carefully processed leading/trailing whitespace
such that when joining all fragments, things will look correct without having to add any extra whitespace.

The common parts to the `parser` and `parser-next` namespaces.