#88 add custom text box to excel skeleton

[jckwik]

As a solution to #88 I've created a custom text box for our excel skeleton. The features include the following:

• Just load the text box once and the text box takes care of its own management
• The text box has a number on it to track how many times you have entered input (1-6) and automatically closes after 6 entries, clicking cancel, or clicking OK with nothing in the box
• Handles multiple inputs on newlines, allowing for mass data entry for testing (tested up to 300 lines)
• (Recent bugfix) Handles one line of input and a newline character as one line of input
• (Known issue) Errors on no input and a newline character

I wasn't able to make a branch directly in the base repo, so my suggestion would be do so and edit this PR to point there so that you're not immediately overwriting main, or else I can make another commit with the skeleton as a different name.