Stale bot updated
This is an updated version of the stale bot.

**It is easier to review the file than the diff, you can find the file [here](https://github.com/huggingface/transformers/blob/d1e516ea0fe9e641a75a89e5a7522392f7dbd59d/scripts/stale.py).**

It sends a warning message after 23 days of inactivity, and closes the issue/PR if no activity is detected in the following 7 days.

It ignores the following labels (case insensitive):
- `Good First Issue`
- `Good Second Issue`
- `Feature Request`
- `New Model`
- `WIP`

If there are assignees on the issue/PR, then it puts the following comment: `f"This issue has been stale for a while, ping @{assignee.login}"`

I propose to leave the PR like it is, and I'll push an empty commit daily to check the result of the stale bot test (I'll remove other tests to ensure that we don't spend unnecessary CI credits). Once we verify that it works as expected for a few days, I propose to merge it.

You may check the results of the first run here: https://github.com/huggingface/transformers/runs/2045189559?check_suite_focus=true (Second commit was rate limited)
@stas00, @sgugger, please review this PR. Here is a visualization of what would be done by the bot, were it to be merged today: https://github.com/huggingface/transformers/pull/10562/checks?check_run_id=2113061781

I have verified that all 11 issues that would be closed have received a warning 10 days ago. Thank you.