v2022.08.18

## What's Changed
* Mismatched ruby versions - updated to 2.6.9 by @2600box in https://github.com/huginn/huginn/pull/3058
* Drop BasecampAgent by @knu in https://github.com/huginn/huginn/pull/3056
* made mysql flush appear as code by @2600box in https://github.com/huginn/huginn/pull/3059
* Migrate from RR to RSpec Mocks  by @knu in https://github.com/huginn/huginn/pull/3066
* fix error 'tried to create Proc object without a block' in Gemfile by @JaHIY in https://github.com/huginn/huginn/pull/3097
* Upgrade mini_racer to the latest version by @knu in https://github.com/huginn/huginn/pull/3103
* Add a Liquid variable referring to the agent itself as `_agent_` by @knu in https://github.com/huginn/huginn/pull/3104
* Force setup_heroku to use heroku-18 stack by @nighthawk in https://github.com/huginn/huginn/pull/3124
* Update gems for ruby 2.7 by @knu in https://github.com/huginn/huginn/pull/3130
* Upgrade Ruby to 2.7 by @knu in https://github.com/huginn/huginn/pull/3055
* Fix ImapFolderAgent documentation regarding mime_types by @axsuul in https://github.com/huginn/huginn/pull/3146

## New Contributors
* @2600box made their first contribution in https://github.com/huginn/huginn/pull/3058
* @JaHIY made their first contribution in https://github.com/huginn/huginn/pull/3097
* @nighthawk made their first contribution in https://github.com/huginn/huginn/pull/3124

**Full Changelog**: https://github.com/huginn/huginn/compare/v2022.01.04...v2022.08.18