The .words file is used by gospel (v1.2+), which wraps the Hunspell libraries
but populates the dictionary with identifiers from the Go source.

<https://github.com/kortschak/gospel>

Alas, no comments are allowed in the .words file and newer versions of gospel
error out on seeing them.  This is really a hunspell restriction.

We assume en_US hunspell dictionaries are installed and used.
The /AFFIXRULES are defined in en_US.aff (eg: /usr/share/hunspell/en_US.aff)
Invoke `hunspell -D` to see the actual locations.

Words which are in the base dictionary can't have extra affix rules added to
them, so we have to start with the affixed variant we want to add.
Thus `creds` rather than `cred/S` and so on.

So we can't use receive/DRSZGBU, adding 'U', to allow unreceive and variants,
we have to use unreceive as the stem.

We can't define our own affix or compound rules,
to capture rfc\d{3,} or 0x[0-9A-Fa-f]{2}

The spelling tokenizer doesn't take "permessage-deflate" as allowing for ...
"permessage-deflate", which is an RFC7692 registered extension for websockets.
We have to explicitly list "permessage".