🪲 Escape internal var used in repeat

[boryanagoncharenko]

Fixes #5255
The internal variable i used in repeat statements is now escaped with the __ prefix, so that it does not show in the output window.

How to test

• Run Hedy locally and run the following snippets for the specified levels. Ensure that the i variable does not appear in the blue variables list in the upper right corner of the output window:

Level 7:

options is 1, 2, 3, 4, 5
repeat 5 times print options at random

Level 8:

options is 1, 2, 3, 4, 5
repeat 5 times
  print options at random

[jpelay]

Works!

[mergify]

Thank you for contributing! Your pull request is now going on the merge train (choo choo! Do not click update from main anymore, and be sure to allow changes to be pushed to your fork).

[mergify]

Thank you for contributing! Your pull request is now going on the merge train (choo choo! Do not click update from main anymore, and be sure to allow changes to be pushed to your fork).