Feature: Versioned dictionaries

Currently, by default check-spelling retrieves https://github.com/check-spelling/check-spelling/blob/dictionary/dict.txt and then consumers can replace (using dictionary) or augment (allow) / redact (reject) additional words.

I plan to make to changes:

1. Only download the dictionary if users aren't supplying their own (using dictionary)
2. Give the dictionary a tag and have each release download a release pinned version

Going forward, this will enable me to update the dictionary by, e.g. removing Archaic words or adding words that are commonly used by consumers.

When I make such updates, I'll be able to include the list of changes in the release notes 😄

🛠️ This is ready for release in 0.0.17-alpha