Add mise.gitignore

[scop]

Reasons for making this change:

I'm a mise user. Local mise configs should not be checked into git.

The upstream project spells "mise" consistently in lowercase, therefore I opted to add the file in all lowercase, too.

Links to documentation supporting these rule changes:

See comments in the added .gitignore

If this is a new template:

• Link to application or project’s homepage: https://mise.jdx.dev/

[scop]

FYI @jdx

[scop]

Rebased, updated links and current set of filenames. I wonder if there's anything I could do to nudge this forward?

[github-actions[bot]]

This PR is stale because there have been no updates in 90 days. It will close after 180 days of inactivity. Leave a comment if you want to keep it open :smile:

[jdx]

Keep it open!