doc: add missing periods in documentation.md

[vsemozhetbyt]

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• documentation is changed or added
• commit message follows commit guidelines

Our MD-2-HTML converter replaces line breaks with spaces in these fragments so the result becomes less readable after that without periods.

Before this PR:

After this PR:

[vsemozhetbyt]

Node.js Collaborators, please, add 👍 here if you approve fast-tracking.

[vsemozhetbyt]

CI-lite: https://ci.nodejs.org/job/node-test-pull-request-lite/648/

[Trott]

Since it will be rendered without a line break, I wonder if it makes sense to remove the line break in the .md file too? Otherwise, what's to stop someone (probably me!) coming along in 6 months and opening a fast-track pull request to remove these "unnecessary" periods? :-D

[vsemozhetbyt]

Amended.
@Trott, @tniessen, is this still LG to you?
CI-lite: https://ci.nodejs.org/job/node-test-pull-request-lite/651/

[tniessen]

Stylistically, I prefer the previous version with a line break, but @Trott's argumentation is plausible.

[Trott]

Separate PR for sure, but I would be all for shortening these blobs of text. For example, the first one would probably be more readable and effective like this:

Stability: 0 - Deprecated. Use of this feature may cause warnings to be emitted.
Backwards compatibility across major versions should not be expected.

(The removed text just basically says what it is already adequately communicated by the word "Deprecated".)

That sort of change is likely to generate bike-shedding, though, so definitely separate PR. :-D

[vsemozhetbyt]

Landed in 2553377
Thanks for the reviews.