Migrate issues and PRs from stretch upstream

[alice-i-cecile]

Upstream is abandoned, so we should investigate any relevant open issues and PRs, and migrate them here as is appropriate.

[alice-i-cecile]

Candidate issues:

• Possible divergence from Chrome? vislyhq/stretch#90
• Does stretch also have this flexbox bug? vislyhq/stretch#89
• LICENSE file is not being included in package upload vislyhq/stretch#84
• Support for Swift package manager? vislyhq/stretch#80
• [Documentation] Example of the code for Rust does not compile  vislyhq/stretch#74
• make dependencies optional vislyhq/stretch#73
• Deep nesting results in poor performance vislyhq/stretch#71
• [Feature] Support async functions in rust vislyhq/stretch#69
• [Feature] Support CSS Grid vislyhq/stretch#63
• (Javascript) stretch dimension of flex children is zero vislyhq/stretch#59
• How to work with leaf nodes? vislyhq/stretch#50
• [JS][notice me senpai ◕‿◕] child node position not being set vislyhq/stretch#57

These are often pretty low-quality, so we should revisit and define them properly.

Potential PRs:

• Include LICENSE file in the published package vislyhq/stretch#97
• Fix the license entry in Cargo.toml vislyhq/stretch#85
• Fix typo in documentation vislyhq/stretch#78
• Update rust.mdx vislyhq/stretch#75

[alice-i-cecile]

Closing this out; I don't think there's anything critical left now.