Bump to version 4.0.0

Version 3.3.7

Upgrade to Webmention 7.0.0 and add support for OpenSSL 3.

Fixes for Jekyll 4, Ruby 3, and some bugs

Bugs fixed:

* Remove deprecated calls to URI.encode (8a66953)
* Fix crash when no webmention config block is specified (63c4087)
* Properly encode URI when calling out to webmention.io (85c6b7d)

Implemented enhancements:

* Jekyll 4 support (a6c4178)

tag v3.3.5

tag v3.3.4

tag v3.3.3

tag v3.3.2

tag v3.3.1

tag v3.3.0

tag v3.1.0