Document the process for adding ADD_TO_PROJECT_PAT token

[qartik]

The action is described at https://github.com/CQCL/hugrverse-actions#add-to-project but it's not clear who/where to look for this token per project.

[ss2165]

Steps:

1. Log in as hugrbot (contact @ss2165 or @aborgna-q)
2. Go to settings/developer settings/personal access tokens
3. Create a new token owned by quantinuum-dev which has no repository permissions and read/write permissions to Projects

[aborgna-q]

I added a clarification to the "token permissions" section in the README, #34.

Most cases should be able covered by what seyon mentions. If the repo is private then we still need a classical token due to add-to-project/issues#632.

[qartik]

Steps:

1. Log in as hugrbot (contact @ss2165 or @aborgna-q)
2. Go to settings/developer settings/personal access tokens
3. Create a new token owned by quantinuum-dev which has no repository permissions and read/write permissions to Projects

These steps and people with access are best suited at hugrverse repo moving the issue there (can't transfer the issue across orgs).

[aborgna-q]

Added an issue over there.