jslint: remove whitespaces using simple regex

Replacing obsolete for loop with a simple regex to remove whitespaces, if a line contains only whitespace.
updated regex to catch spaces and tabs only

seems to be cleaner, also other "weird whitespace characters" in an isolated line will be flagged as an error by jslint
Update 'Extension Ideas' query link so it shows both open & closed issues,
instead of closed only - the new GH query syntax now permits this.
Merge pull request #8698 from adobe/pflynn/extension-ideas-link

Improve 'Extension Ideas' query link in CONTRIBUTING.md docs
Merge pull request #8674 from MartinMa/master

jslint: remove whitespaces using simple regex