Sopel-github

Changed:
* Require Sopel 7.x and use its features (58, 61)
* Ignore lines that look like (HTML) comments or headings when shortening
comment bodies (57)
* Deprecated query string API authentication replaced by HTTP Basic Auth (62)

Fixed:
* Handle missing user information in commit data (59)

Fixed:
* Syntax error in webhook code

Added:
* Error handler in webhook authorization (51)

Fixed:
* Wrong config value access in webhook authorization (51)

Fixed:
* Comments with trailing whitespace incorrectly had `[…]` appended even if the
body contained only one line of (non-quoted) text (50)

Changed:
* Milestone name is now included in `demilestoned` webhook events (46)
* GitHub originally didn't include this information in the webhook payload,
but started sending it in approximately late-summer 2019

Fixed:
* Comments that were not truncated would still have `[…]` appended if the
comment body included quoted text (47)

Changed:
* Comment bodies will be shortened to approx. 250 characters, to try and stay
within the length limit of one IRC line (45)

Fixed:
* Repo URLs can be detected even with leading text on the line (44)