Release co-ordination for 2.8.0

2.7.0 is more than a years old, since then, there are some new, awesome features in the 2.x branch, like https://gitlab.com/DMore/chrome-mink-driver/-/merge_requests/79 ;P

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• Update CHANGELOG for 2.7.0 and 2.8.0 (!96 (merged))
• Review & merge CHANGELOG (!96 (merged))
• Review and merge code style checks in CI (!95 (merged))
• Document release process
• Fix CI again (#106 (closed), !102 (merged))
• Swap from sensiolabs/security-checker to enlightn/security-checker (#107 (closed), !103 (merged))
• Check if this test runs in CI (per this comment); it appears to not run.

CHANGELOG

• Enforce coding standards in CI (!95 (merged))
• Improved support for Behat 1.8.x, fixes to CI (!93 (merged), #94 (closed), #104 (closed))
• Support obtaining event listeners for elements (!91 (merged))
• Correctly use configured DevTools connection URL (!90 (merged), #93 (closed))
• Re-throw dead connection exceptions (!88 (merged))
• Support setValue() on 'url' input types (!87 (merged))
• Support clearing and retrieval of messages from console.log (!86 (merged), #97 (closed))
• Support multiple file attachments (!83 (merged))
• Support non-HTML responses (!78 (merged))
• Updated Event dispatching for input change to add support for React components (!74 (merged))
• Full page and screen screenshot functionality (!72 (merged), !79 (merged))
• Improve exception message on Chrome error (!71 (merged))
• Handle experimental Page.navigatedWithinDocument (!70 (merged))