Make a consolidated grammar appendix.

[ehuss]

There should be an automated script which consolidates the grammar into an appendix.

Also, every grammar rule should have a link to its definition (even if it is on the same page). Will need to figure out a way to add <a> anchors to each rule. I think Braulio had a script for this. Also, it would be nice if the rule highlighted when selected.

Braulio had a script for doing this, may be useful to get started: https://github.com/brauliobz/rust-reference/tree/grammar_join