Add ability to self-publish DIDs as statically hosted content on e.g. personal websites, Github pages, etc using CLI tool.

[vdods]

See #18

Add:

• Ability to self-publish DIDs by generating all the files expected of a VDR on a website serving only static content, e.g. Apache, Github pages, Gitlab pages, etc.
• This should include ability to manage and execute webhooks based on DID updates.
• Github actions to run the CLI tool to self-host VDR on one's Github pages. Similar for Gitlab pages.

[vdods]

Update: The filesystem mapping now only consists of one file: did-documents.jsonl, and a DID update simply gets appended to it with a newline. The CLI tool does need to support this form of "DID doc store" -- to be able to read it in, verify it, produce updates, and then append to the file.