chore(changelog): add test for addition of trailing newline

[gkalpak]

Adds tests for the functionality added by #9550.

(As suggested in #9550 (comment) .)

[googlebot]

CLAs look good, thanks!

[caitp]

are we actually able to run these tests anymore? node_modules/.bin/jasmine-node changelog.spec.js throws --- some problem loading the lunr.js test helper, which we apparently need?

[gkalpak]

I don't think we need the lunr helper.
I was able to run the tests using jasmine-node's --nohelpers switch:

jasmine-node --nohelpers changelog.spec.js

[caitp]

weird, huh

[caitp]

anyway, land it I guess, it looks okay to me

[caitp]

wait, actually no --- one of these tests fails

[gkalpak]

I had a not in the expectation that shouldn't be there. Fixed.
_{(It was a left-over from my testing that the tests are actually executed 😄)}

[caitp]

yep, just tried it and it's green, lgtm

[caitp]

merg'd

[caitp]

in the future, commits which are just tests use the test(....): ... notation, per the commit message guidelines --- but it doesn't matter much