Document recommended best practices for Package Authors

**Describe the problem/challenge you have**
For a new package author, they can read the current kapp-controller to understand how to create a package and then distribute it in a package repository bundle. However, since they are new, they might benefit from a dedicated docs page that talks about the recommended best practices that they should follow.

**Describe the solution you'd like**
Create a dedicated docs page for recommended best practices for Package Authors. Few of the things that can be a part of this doc:
- [ ] Recommended list of metadata for packages such as icon, description, categories, release notes, etc. Most of this metadata is not required by the APIs, however, it would be helpful to document the recommended ones that will help the consumers of the packages.
- [ ] The best practices for versioning the packages.
- [ ] The best practices to create package repository bundles and how to update them when new packages are available.

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