Err-stackstorm

Added
- support for slackv3 backend and passing action-alias extra parameters as Slack block or attachment.
- documentation to use Slack blocks or attachments.
- tests for Python from 3.6 to 3.10

Changed
- hard coded notification_route to use user configured route when calling match_and_execute.

Removed
- logging sensitive api tokens in debug logs.
- "<action-alias>" for action execution help text.

Added
- Session are deleted automatically when a chat user fails to authenticate against St2 API.
- Include Slack users "display name" in session list for easier identification.

Changed
- Update documentation with corrections and improved examples.
- Corrected error of dynamic commands not registering correctly when the plugin was deactivated/activated.
- Improved robustness of version check code to gracefully handle github.com being unavailable.

Added
- Added err-stackstorm version in the st2help display.

Changed
- Fixed st2help function to have to correct number of positional arguments.

Added
- Added CircleCI build badge to README.
- Added route key to be defined by user to allow mutliple bots attached to a single StackStorm instance.
- Added version check on start-up to log if newer version of the plugin are available.

Changed
- Updated curl example in troubleshooting section.
- Changed all bot commands to be registered dynamically to allow user defined plugin prefix.

Added
- Added configuration for mattermost, rocketchat, discord, gitter and slack to docker build.

Changed
- Improved Discord Chat Adapter formatting.
- Corrected configuration name handling which caused exceptions to be raised.
- Updated documentation to direct readers to readthedocs.

Removed
- Removed old readme file.

Added
- Added `deactivate` method to correctly handle errbot reload and stop process.
- Added initial files for documentation to be served on readthedocs.
- Added missing documentation for nginx configuration when using Client-side authentication.
- Added support for IRC and Discord Chat Adapters.
- Added source documentation for ReadTheDocs.

Changed
- Correctly detect when the `extra` attribute is passed to the Slack Chat Adapter.
- Send web login form data as JSON to be compatible with errbot >=v6.0.

Removed