(core) For autocomplete suggestions in formulas, add links to suggestions we have documentation for.

Summary:
This is a hacky solution that unfortunately relies on internal workings of ACE
autocomplete popups. I don't see a less hacky one if we stick with ACE
autocomplete.

Test Plan: Added a test case for links to test/nbrowser/Formulas.ts

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2610

sandbox/grist/autocomplete_context.py

@@ -78,6 +78,8 @@ class AutocompleteContext(object):
       if completion:
         # For methods (eg ".lookupOne"), use the original result as funcname (eg "Foo.lookupOne").
         if dot >= 0:
+          varname = funcname[:dot]
+          funcname = self._lowercase.get(varname, varname) + key
           completion = completion._replace(funcname=funcname)
         return tuple(completion)