Feature request: minimum thresholds for table inclusion

**Is your feature request related to a problem? Please describe.**

I get a lot of one-or-two-time `good first issue` contributions from folks new to my repos. Those contributions are nice to see, but most of those contributors don't stick around. So it ends up that much of my contributor tables are filled by people who've done only a couple things a while ago.

**Describe the solution you'd like**

It'd be nice to have the table only show contributors above some configurable threshold(s). The most straightforward path would be allow a configurable minimum number of contributions: `1` by default.

```jsonc
// .all-contributorsrc
{
// ...
"minimumContributions": 2,
// ...
}
```

**Describe alternatives you've considered**

Just brainstorming:

* Requiring a minimum number of _types_ of contributions
* Having multiple thresholds: e.g. requiring 2 contributions once there are >=20 contributors
* Limiting the contributors shown to the top X number of contributions
* Requiring a label exist or not exist:
* Exist example: adding a `allcontributors-accepted` kind of label
* e.g. preventing `good first issue` issues from counting towards the table
* Having multiple tables: a first/primary one for highest contributors, and followups for lower thresholds

**Additional context**

The bot would probably want to be updated to give a mention for why a person's contribution was or wasn't yet eligible for the table.