Create add-to-inbox.yml for adding new issues to the project board

[joshblack]

We have this workflow set up in other repos on Primer so that technical issues can show up in our project board to better manage support. This PR adds this workflow to this project so that octicons issues can be added to this board with the corresponding labels.

[changeset-bot]

⚠️ No Changeset found

Latest commit: a4098ca

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR