- zed-extensions/elixir#61 renames `HEEX` to `HEEx`; to prevent any
disruptions from that change, this adds the correct name alongside a
settings migration
- zed-extensions/elixir#101 adds support for `EEx` templates; this sets
the default language server to be the same as that of `Elixir` and
`HEEx`

This also adds a few more extensions that should be recognized as `HEEx`
files

Release Notes:

- N/A

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Co-authored-by: Finn Evers <finn@zed.dev>