Package list: ignore modifier key press

[tkohlmeier]

• I have read the contributing guidelines, and I agree with the Code of Conduct.
• Have you checked that there aren't other open pull requests for the same changes?
• Have you tested that the committed code can be executed without errors?
• This PR is not composed of garbage changes used to farm GitHub activity to enter potential Crypto AirDrops.
  Any user suspected of farming GitHub activity with crypto purposes will get banned. Submitting broken code wastes the contributors' time, who have to spend their free time reviewing, fixing, and testing code that does not even compile breaks other features, or does not introduce any useful changes. I appreciate your understanding.

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Currently, pressing Control, Shift or Alt key results in selecting the first item in a package list. This PR fixes this by only handling [a-z0-9] keys.

[Martí Climent (marticliment)]

Will test and merge later

[tkohlmeier]

Found an even better solution. The CharacterReceived event seems to be exactly what is needed here.

[mrixner]

Yeah, I kind of patched this together. Thank you for improving it!