The milestone filter doesn't appear to work in gh version 0.11.0 (2020-07-16)

For example on https://github.com/Safecast/safecastapi/milestone/4

I can see the issue by author

❯ gh issue list -A seanbonner | grep backup
89	OPEN	Need How To restore from backup		2019-06-12 03:23:13 +0000 UTC

But not by milestone

 ❯ gh issue list --milestone 'AWS Migration'

No issues match your search in Safecast/safecastapi

Originally posted by @matschaffer in #641 (comment)

Props to @BondAnthony who pointed this out in the original PR, but we haven't spotted it; sorry!

I think our --milestone filter should work like this:

• if a number is passed, use it as milestone ID;
• if a non-number is passed, look up all milestones and resolve it to an ID. This is how I expected the GitHub API to behave, but apparently it only takes IDs and special values such as null and *.

/cc @eddumelendez