234|UI: Session menu

Description of change

• Added Session menu to start new, save, update, manage timeline or reviews and quit.
• Stax button moved to left.

How to test it

Read the doc: https://superprod.gitlab.io/-/stax_suite/stax/-/jobs/1113315114/artifacts/docs/build/html/getting_started.html#session

Checklist

Please check if your MR fulfills the following requirements:

• Documentation have been updated, if needed
• Build was run locally and any changes were pushed
• Lint has passed locally without error
• CHANGELOG.md have been updated, if needed

FYI: @dddjef