Create test strategy for Real-Time preview for wikitext.
Example test strategy from another project: https://www.mediawiki.org/wiki/User:DWalden_(WMF)/Copy_paste_diffs
Acceptance criteria:
- Strategy is a living breathing artifact which includes testing instructions, oracles (i.e., how we recognize potential bugs), test ideas, and any open questions
- Strategy is documented in a place CommTech team can access