Uplift documentation to comply with Vale rules

## Background

#242 added Vale tooling to the repository to ensure documentation consistency. It is currently disabled from preventing merging, so it is for information only.

To see the scale of what is outstanding in Vale:

```bash
$ cd sdk
$ make vale-errors | wc -l
make: *** [Makefile:56: run-vale] Error 1
203
$ make vale-suggestions | wc -l
make: *** [Makefile:56: run-vale] Error 1
806
```

## Task

* Review rule output and make it comply with Vale rules.
* Enable Vale rule enforcement in CI, such that Value errors are not permitted.