CHI-3523: Aselo Webchat React App POC

[stephenhand]

Description

This POC ports the front end only into the flex plugin repo, and it can only be run locally, but works end to end on Aselo Dev

A follow on PR #3724 shows the next step where we migrate some back end functions as well, which will probably be required to support calling custom stuff from the client

Checklist

• Corresponding issue has been opened
• New tests added
• Feature flags added
• Strings are localized
• Tested for chat contacts
• Tested for call contacts

Other Related Issues

None

Verification steps

AFTER YOU MERGE

1. Cut a release tag using the Github workflow. Wait for it to complete and notify in the #aselo-deploys Slack channel.
2. Comment on the ticket with the release tag version AND any additional instructions required to configure an environment to test the changes.
3. Only then move the ticket into the QA column in JIRA

You are responsible for ensuring the above steps are completed. If you move a ticket into QA without advising what version to test, the QA team will assume the latest tag has the changes. If it does not, the following confusion is on you! :-P