One time tokens for app/bot usage in opentelemetry.io repo

[svrnm]

We want to re-enable the /fix:* commands for the opentelemetry.io repo. To do so in a secure manner, we need one time tokens (similar to GITHUB_TOKEN) which are provided by a bot, otherwise a push to the repo will not trigger follow-up github actions as this is disabled by GH.

cc @open-telemetry/project-infra

[adrielp]

This sounds like it would be a good use case for octo-sts @trask