Add ability to auto complete attribute quotes

[jzyrobert]

This is a popular requested feature on VS code

Given some valid version of
<tag foo= ....
Either "" or '' should be inserted and the cursor moved into the middle, in order to avoid another unnecessary character, as attribute values (almost?) always require quotes.

[AamirSohailKmAs]

@aeschli This issue is resolved in the linked PR. It needs manual closure since the PR lacked the automatic closure keywords.