Docs review

Complete review pass of `docs` branch.

Mainly fixing spelling and typos but some more debatable rewordings included so no blind commits please :)
@forki Its a line you already had that I was attempting to bring out even more. Perhaps it should be:

> NB The filename `build.cmd` (which is used as the name for the snippet above) is listed in the `.gitignore` file. 

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