Support for multiple source paths

When generating docs for the operator with mutliple CRDs in different paths, it would be nice to specify multiple source paths. For ex, in the following folder structure -

```
api
- crd1
- crd2
- common
```

`common` contains shared structs used by both crd1 and crd2 CRDs. To generate adocs for crd1, I would have to pass folders `crd1` and `common`. Similarly `crd2` and `common` folders if I want docs for crd2.

I looked at the code that parses the source paths (processor/processor.go) and found out that the controller-tools has a `LoadRoots` api that supports reading from multiple source paths. So it shouldnt be too complex to support multiple source paths.

As a workaround to this problem, we are using config.yaml to exclude types in each adoc.