Support policy

[tomherni]

There should be a support policy for browsers and runtimes, and perhaps also other tools such as TypeScript.

Common policies support 2 major versions or 2 years back. QuoteQuote already meets this criteria.

Relevant information:

• QuoteQuote uses negative lookbehind assertions. (Support since 2017–2020, with the exception of Safari in March, 2023.)
• QuoteQuote uses unicode character class escapes in unicode-aware mode. (Support since 2018–2020.)
• QuoteQuote ships ES2022. Consumers can use a compiler to ship earlier versions.