[HTML] Improvements to attribute completions (#2433)

* [HTML] Allow the user to type > at the end of a tag to "overwrite"

If for some reason a user wants a second >, they can press that key
twice.

* [HTML] Improve attribute completion flow

Always adds a field to attribute completions to provide a better typing
experience for users. This allows the user to press [tab] instead of
typing a close quote, or close quote and greater than symbol.

HTML/Default.sublime-keymap

@@ -0,0 +1,9 @@
+[
+	{ "keys": [">"], "command": "move", "args": {"by": "characters", "forward": true}, "context":
+		[
+			{ "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
+			{ "key": "following_text", "operator": "regex_contains", "operand": "^>", "match_all": true },
+			{ "key": "selector", "operator": "equal", "operand": "punctuation.definition.tag.end.html", "match_all": true },
+		]
+	},
+]

HTML/html_completions.py

@@ -582,6 +582,9 @@ def attribute_completions(self, view, pt, prefix):
             # add a space if not there
             suffix = ' '
 
+        # ensure the user can always tab to the end of the completion
+        suffix += '$0'
+
         # got the tag, now find all attributes that match
         return sublime.CompletionList(
             [