Insert missing spaces after sentence periods, commata & abbreviation

Why is this change being made?

A few more minor style issues I noticed while reading during the onboarding.

FYI @aqualls: I started with the first rule in GL/doc/.vale/gitlab/SentenceSpacing.yml, but modified it to \ ([A-Z]{2,}|[a-z]+)[.?!,][A-Z][a-z]+\ to catch all these cases (with a few false-positives like "Introduce docker.Client timeouts" & "Leverage version.Gitlab to …"). Possibly a useful update to the Vale rule?

Does this MR meet the acceptance criteria?

Assign to DRI

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what