Use standard requirement level words

[surchs]

Description

To the extent that our docs describe a standard or requirements that people have to follow to use our tools, we should also use standard language to indicate the requirements.

The de facto standard is https://www.rfc-editor.org/rfc/rfc2119.html, so I propose that we go through our docs and specify the current wording with the standardised terms where needed

Relevant documentation pages

everything

Additional details

No response

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