[llvm] [docs] Update the commit review admin task with process details (PR #210420)

[Reid Kleckner via llvm-commits]

================
@@ -1,5 +1,22 @@
 # LLVM Admin Tasks
 
+## Grant Commit Access
+
+- Frequency: Ongoing
+- Permissions: Admin
+- Description: An admin should periodically review the list of commit access requests.
+
+This can be done by searching for issues in the llvm-project repository which have the [`infra:commit-access-request` label].
+Any user that meets the [commit access requirements] should be added to the ['LLVM Committers' team].
+The admin should add a comment to the issue when an invite to join the team has been sent and then close the issue when the invite has been accepted.
+Admins should close issues after sending the invite and invite the requestor to reopen if there are issues.
+If there are insufficient votes and it has been over five days since the last update, admins should remove the `infra:commit-access-request` label.
----------------
rnk wrote:

We did not pick a duration. I had to come up with a number when writing policy. I'll soften this to "may" instead of "should" and extend it to two weeks to give more wiggle room. I hope we have fewer than 10 applications a week, that should keep the dashboard manageable.

https://github.com/llvm/llvm-project/pull/210420