An NX plugin support

Hey @ai thanks for this awesome tool,

I've found myself integrating it in an NX monorepo manually first by adding the configuration file per each project and afterwards by adding the following target for each project (for enable execution)

```json
"size-limit": {
"executor": "nx:run-commands",
"options": {
"cwd": "apps/app1",
"commands": [
"size-limit"
]
}
}
```
So after 2 projects I decided to automate it by creating an NX community plugin 😄
I'll really appreciate if you could peek in the [docs ](https://github.com/LironHazan/nx-size-limit/tree/main/packages/nx-size-limit) I've supplied and share your feedback to make sure it fits the size-limit "go to" approach,
I've tried to make it as less opinionated as possible :)

Thanks! 🚀