CLI Maven Plugin implementation

Hey there,
just recently found out about all-contributors and really liked the idea, but personally, the bot would cause too much webhook/commit history spam and as a Java developer the node-based CLI is also rather unhelpful. So I wrote a Java Maven Plugin that simulates the updating of the README.md using the .all-contributorsrc and that can be called via Maven or gets called during each build.
https://github.com/tr7zw/all-contributors-maven/
During setting-up I was kinda disappointed that most of the contribution links point into nowhere, so I added the ability to give each contributor a link mapping that allows to overwrite the URL.
```
"contributions": [
"infra"
],
"links": {
"infra": "https://example.com/"
}
```
(Not sure if I just missed something there, but I guess this is fine)
In the end, I implemented it for my open source project and it works/looks really good.
https://github.com/tr7zw/Item-NBT-API
Maybe you guys could take a look at it and give some feedback 👍