.html files were recognised before -- the name was shown on
the statusbar, but it didn't actually enable the syntax highlighting.
This also sneaks a highlighting for JSON using JS highlighting.
It isn't technically correct, but so does TextEditor. :^)
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
