chore: clarify criteria for 'easy' label

[dagurtomas]

[mcdoll]

Thanks. I think it is good to clarify this. There might be cases where a theorem gets generalized at almost no cost and I would consider that easy, but it is probably better to slightly more strict on that label.

[chrisflav]

Do we even need an easy label? Is it something people specifically filter PRs by?

[bryangingechen]

Do we even need an easy label? Is it something people specifically filter PRs by?

I've often used it when looking for low-hanging fruit to approve.

[chrisflav]

I am wondering if it is sensible to only allow usage of the easy label for experienced contributors. It seems to me that in particular new contributors are overusing easy.