Add tag wrapping key

[benjervis]

Last additional keybinding (probably) before attempting CodeMirror 6, pressing CmdShift,(or, on Windows, CtrlShift,) will wrap the currently selected text in an empty fragment that is ready to be typed in.

All keyboard shortcuts are now shown in a legend in the settings panel.

This required a slight reworking of the light mode colour palette, updating gray2 and making neutral not some dark grey.

Also adds some util help for preloading the code panel with content during a cypress test, with an optional param to loadPlayroom.

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🦋 Changeset detected

Latest commit: 525fe3102769cc5617486bd0502e728649e7c565

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | -------- | ----- | | playroom | Minor |

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[mrm007]

Here's what I had in mind: https://github.com/seek-oss/playroom/commit/652289a20579a1508105a3426e33a5f12f3f512a

Try it out: https://playroom--5d1645e7ff3a95b4f9f5d4b124342eb3b78d7144.surge.sh/

[benjervis]

@mrm007 I see what you were going for, but I think the tradeoff here between DRY-ness and readability isn't quite working for me. It's a bit more chaotic, and quite disconnected from the single use case of the description in the settings panel.

There's a couple of other good cleanups in there though, I'll bring a few of those across.