Add new documentation concerning icons

[mririgoyen]

Proposed change

Icons are a large part of Home Assistant, however we have little information in our official documentation about them. In this PR I have added a dedicated page to frontend icons that provides our users with information on how to find icons, suggest new icons and aliases, and even contribute icons to the MDI project!

Additionally, I have updated the Frontend landing page.

---

This is only a first stage. I would like to expand on the icon documentation by adding another page with a curated list of icons by entity category in the future. However, that will require getting MDI into the docs site (replacing Font Awesome), which I have started to do in another branch.

Type of change

• [ ] Spelling, grammar or other readability improvements (current branch).
• [x] Adjusted missing or incorrect information in the current documentation (current branch).
• [ ] Added documentation for a new integration I'm adding to Home Assistant (next branch).
  • [ ] I've opened up a PR to add logo's and icons in Brands repository.
• [ ] Added documentation for a new feature I'm adding to Home Assistant (next branch).
• [ ] Removed stale or deprecated documentation.

Additional information

• Link to parent pull request in the codebase:
• Link to parent pull request in the Brands repository:
• This PR fixes or closes issue: fixes #

Checklist

• [x] This PR uses the correct branch, based on one of the following:
  • I made a change to the existing documentation and used the current branch.
  • I made a change that is related to an upcoming version of Home Assistant and used the next branch.
• [x] The documentation follows the Home Assistant documentation standards.

[github-actions[bot]]

There hasn't been any activity on this pull request recently. This pull request has been automatically marked as stale because of that and will be closed if no further activity occurs within 7 days. Thank you for your contributions.

[frenck]

Do not close to this one little bot... this is waiting for us to review it

[github-actions[bot]]

There hasn't been any activity on this pull request recently. This pull request has been automatically marked as stale because of that and will be closed if no further activity occurs within 7 days. Thank you for your contributions.

[mririgoyen]

@frenck Stale again. Anything I can do to help move this along?

[github-actions[bot]]

There hasn't been any activity on this pull request recently. This pull request has been automatically marked as stale because of that and will be closed if no further activity occurs within 7 days. Thank you for your contributions.

[frenck]

still relevant stale bot, don't close :)

[github-actions[bot]]

There hasn't been any activity on this pull request recently. This pull request has been automatically marked as stale because of that and will be closed if no further activity occurs within 7 days. Thank you for your contributions.

[frenck]

still not stale bot

[mririgoyen]

@frenck We just actually deprecated the MDI website and some of the URLs and info here are outdated. Let me update this in a couple hours before you fully merge.