fix #2549 -- no reuse BIF names

- fixed docs to not demonstrate reuse of built-in function
  names "str" and "int", even when within a one-off script

- note: did *not* change the "str" and "int" shown in
  Howto/Starting/Part1/Learning-Typeclasses.md file,
  as those are class variables (i.e., Character.str and
  Character.int), which does not replace the BIFs of
  str() and int(). Therefore, methods inside the class
  can still use the python BIFs. While this is possibly
  confusing to new python programmers, it is also not
  within the scope of #2549.

misc edits:
- add .vscode/ to gitignore

.gitignore

@@ -53,3 +53,6 @@ docs/build
 
 # For users of Atom
 .remote-sync.json
+
+# Visual Studio Code (VS-Code)
+.vscode/