Add support for generic text searching

[kkoreilly]

Discussed in https://github.com/cogentcore/core/discussions/1317

^{Originally posted by heejit November 16, 2024} How do I search in document ??

[rcoreilly]

really need this in content!

use compile time word2vec vectors and save those for each word used in entire content space; any search word in that dict will work to find multi-word combos that match compile-time paragraph-level vectors from all the words in the param. filter on frequency etc as usual. https://en.wikipedia.org/wiki/Latent_semantic_analysis

can probably get away with short 50 dim vectors, but still that is kinda big overall. need to do more research on other techniques.