Integrate (optionally) with Lucy for indexing

[fgabolde]

This one is a doozy.

For the best results, we'd need

• three Lucy indexes: one for methods and attributes (use PPI to detect Moo(se)-generated methods?), one for the code in general (skip non-sigil punctuation), one for the POD, with highlighting enabled, and backlinks to the generated POD if we can (for methods)
• a copy of the code with the unrendered POD, for the code search result highlights -- we should estimate the size on disk of the resulting files
• an additional pass during indexing for the aforementioned Lucy search indexes
• a better search interface...

All this stuff needs to be optional, which will be an interesting challenge.