[CTIS] Add note that current SEs are unweighted

[nmdefries]

Summary

• Add banner with note that current SEs are unweighted.
• Change weighted indicators link in contingency tables page to properly point to weighting discussion.

[capnrefsmmat]

Huh, we haven't used \( as a math delimiter in this file before, but KaTeX appears to support it, so I guess we can. (And probably should, since apparently it's for inline math and $$ is for display math)

[nmdefries]

I was struggling a lot with getting $$ to display as in-line rather than as a block. Something about being inside of a div?

[capnrefsmmat]

My read of the KaTeX manual is that it treats $$ to mean display (block) math by default. Somehow that works fine in most of the docs. In any case I rendered the documentation with Jekyll and your update looks fine, so I'm fine leaving it as you wrote it.