lint: Add rule for spacing inside Handlebars translation tags.

This commit also includes the fixes to make all Handlebars templates
compliant with the new rule.

tools/linter_lib/custom_check.py

@@ -389,6 +389,8 @@ def build_custom_checkers(by_lang):
     handlebars_rules = html_rules + [
         {'pattern': "[<]script",
          'description': "Do not use inline <script> tags here; put JavaScript in static/js instead."},
+        {'pattern': '{{ t ("|\')',
+         'description': 'There should be no spaces before the "t" in a translation tag.'},
         {'pattern': "{{t '.*' }}[\.\?!]",
          'description': "Period should be part of the translatable string."},
         {'pattern': '{{t ".*" }}[\.\?!]',