✨(frontend) use title first emoji as doc icon in tree

[olaurendeau]

Purpose

This pull request intent to fix this issue.
If the first unicode char of a title is an emoji, this emoji will replace the standard icon in the tree.

Proposal

I have made use of the library emoji-regex, because I didn't find a solution simple enough with a regex which would be compatible with ES5.

I took the liberty to add a make frontend-test command.

E2E Frontend test are failing, not sure it relates to this PR. I also had to increase the GitHub Action timeout so that it complete.

External contributions

Please ensure the following items are checked before submitting your pull request:

• I have read and followed the contributing guidelines
• I have read and agreed to the Code of Conduct
• I have signed off my commits with git commit --signoff (DCO compliance)
• I have signed my commits with my SSH or GPG key (git commit -S)
• My commit messages follow the required format: <gitmoji>(type) title description
• I have added a changelog entry under ## [Unreleased] section (if noticeable change)
• I have added corresponding tests for new features or bug fixes (if applicable)