Updates based on spec mode discussion

[chriskrycho]

@rwjblue or I will try to update this later with details, but I'm starting this issue to capture the notes so we can iterate on it—

• relation of keywords/built-ins w/imports/etc.
• how various embeddings should work
• how whitespace handling should work
• how escaping (e.g. nested <template>, or, notionally in the future, nested <style> or nested <query> etc.) should work

Context: spec notes from 2022/05/10

[NullVoxPopuli]

Is this still relevant?