### What

- Fixes the patch for `wasm-bindgen` output in `build-wasm.mjs`
- The names of some variables changed (e.g. `cachedUint8Memory0` became
`cachedUint8ArrayMemory0`)
- Added an auto-generated file which stores one hash per file from the
_unpatched_ output of `wasm-bindgen`
- If the hash changes, that means the output has changed and the build
will fail
- We currently build the JS package on every PR, so we'll find out then
and there
- Note that the viewer we upload to GCS is _not_ patched, only the JS
package (used in rerun.io/docs and notebooks) is patched.

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7970?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7970?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!
* [x] If have noted any breaking changes to the log API in
`CHANGELOG.md` and the migration guide

- [PR Build Summary](https://build.rerun.io/pr/7970)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

To run all checks from `main`, comment on the PR with `@rerun-bot
full-check`.

Update "Migration Guides" redirect to point to 0.19, so visitors see the
0.19 guide first instead of the 0.18 guide.

Add a reference page for the dataframe APIs.

It's still very barebones at this point because #7819 makes it very
difficult to write snippets for this.

But it is literally infinitely better than what's there right now:
nothing.

- DNM: requires #7817 
- Closes #7828