Continuing my PR series adding features to the Katex implementation, I added support for equation labelling and referencing (more Mathjax compatibility):
I enabled it in the Discourse code too as seen in the commit. This adds support for \tag, \label, \ref, \eqref so equations can be labeled and referenced (references are clickable too). This is another feature that Katex disables by default. Enabling it brings the Katex implementation in DIscourse more inline with Mathjax. My previous PR added support for persistent macros.