Fixed saving new scratchpads to localStorage

[vExcess]

Updated to

• use getKAID function defined in data-util.ts
• use querySelectorPromise
• use userAuthoredContentType from onProgramPage argument
• avoid saving the code to localStorage if we aren't currently on a new scratchpad page

I don't think we need to worry about naming collisions with KA because the extension is storing the same data. Using the same key prevents us from storing duplicate data and wasting memory.

[EthanLuisMcDonough]

Works well on my end. Thanks for the PR.