issue #2243 -- prefer f-strings over %-interpolation

edited docs to prefer f-strings, then str.format(), and remove %-interpolation

additional ad-hoc documentation fixes, as opportunities seen:
- replace Built-In Function (BIF) "min" variable with "mins"
- prefer BIF str(var) over "%s" % var
- reformat some code examples to clarify multiple args passed to functions
- change some single-quote strings to double-quotes for consistency
- fix mismatched parens

misc edits:
- add .vscode/ to gitignore

docs/source/Components/MonitorHandler.md

@@ -50,9 +50,7 @@ def _monitor_callback(fieldname="", obj=None, **kwargs):
         new_value = getattr(obj, fieldname)
     else: # an attribute    
         new_value = obj.attributes.get(fieldname)
-
-    obj.msg("%s.%s changed to '%s'." % \
-                  (obj.key, fieldname, new_value))
+    obj.msg(f"{obj.key}.{fieldname} changed to '{new_value}'.")
 
 # (we could add _some_other_monitor_callback here too)