Add stale.yml

[Raruto]

In order to automatically handle inactive issues:

• add a label "stale" on issues and pull requests after 30 days of inactivity and comment on them
• close the stale issues after 14 days of inactivity
• if an update/comment occur on stale issues or pull requests, the stale label will be removed and the timer will restart

Reference:

• closing inactive issues
• actions/stale

Have a nice Day,
Raruto

[vanling]

@aheinze, I would definitely do something like this. The amount of issues and PR can scare potential new users away.