DOC-2363: Added new `A11ycheckStart`, `A11ycheckStop`, `A11ycheckIgnore`, `A11ycheckRepair` and `A11ycheckShowDetails` events..

[kemister85]

Ticket: DOC-2363

Site: Staging branch- Release notes Site: Staging branch- Events

Changes:

• Added new A11ycheckStart, A11ycheckStop, A11ycheckIgnore, A11ycheckRepair and A11ycheckShowDetails events to a11ychecker.adoc, and added release notes entry for new added events.

Pre-checks:

• [x] Branch prefixed with feature/<version>/, hotfix/<version>/, staging/<version>/, or release/<version>/
• [x] Files has been included where required (if applicable)

Review:

• [x] Documentation Team Lead has reviewed