[Docs] Reorganize folders and sidebar in Docs

### Issue Type

Documentation Improvement

### Description

Looking for input on reorganizing the Docs sidebar and folders. (Contributing not to be changed)

In small PRs, sections will get fixed/added and this will also fix #6188

Adding a Quick Start Guide will be part of the project that will fix [#6190](https://github.com/actualbudget/actual/issues/6190)

Screenshots of sidebar:

### Documentation URL

_No response_

### Documentation Category

_No response_

### Expected/Desired Content

_No response_

### Screenshots or Examples

```bash
See above.
```