Include ConnectionDetailsTypes in the Connection Details documentation

### ConnectionDetail Types

When using XR Pipeline mode, it is required that `ConnectionDetails` are explicitly defined (ex. [0]) with their types which is a change in behaviour from the default mode that allows for details to be define implicitly as per the current documentation [1].

With the Crossplane Function in beta release, I would propose that a section be added to documentation that outlines the available `ConnectionDetailType` types [2] which include:

* `Unknown`
* `FromConnectionSecretKey`
* `FromFieldPath`
* `FromValue`

[0]
```
crossplane: error: cannot render composite resource: pipeline step "base-patch-and-transform" returned a fatal result: invalid Function input: resources[0].connectionDetails[0].type: Required value: connection detail type is required
```
[1] https://github.com/crossplane/docs/blob/master/content/master/concepts/connection-details.md
[2] https://github.com/crossplane/crossplane/blob/eec86c928f62b4b710f7f9db8d411efbc1791a86/apis/apiextensions/v1/composition_types.go#L771