Add scratch-link cask

[bjrbhre]

version '1.3.57'

Scratch Link is a helper application which allows Scratch 3.0 to communicate with hardware peripherals.
Scratch Link replaces the Scratch Device Manager and Scratch Device Plug-in.
It is open-sourced (BSD) since 2019.

The source code is available here
https://github.com/LLK/scratch-link

To learn more about Scratch & Scratch Link go here
https://scratch.mit.edu/microbit

This is also where the zip/pkg download link is provided
https://downloads.scratch.mit.edu/link/mac.zip

Important: Do not tick a checkbox if you haven’t performed its action. Honesty is indispensable for a smooth review process.

After making all changes to a cask, verify:

• brew cask audit --download {{cask_file}} is error-free.
• brew cask style --fix {{cask_file}} reports no offenses.
• There are no open pull requests for the same update.
• The submission is for a stable version or documented exception.

Additionally, if adding a new cask:

• Named the cask according to the token reference.
• brew cask audit --new-cask {{cask_file}} worked successfully.
• brew cask install {{cask_file}} worked successfully.
• brew cask uninstall {{cask_file}} worked successfully.
• Checked the cask was not already refused.
• Checked the cask is submitted to the correct repo.

[bjrbhre]

I've also opened a discussion on scratch-link side to be sure they approved their pkg being available through cask
scratchfoundation/scratch-link#182

[vitorgalvao]

Needs to be submitted to homebrew/cask-drivers. We define drivers as:

Software to make a hardware peripheral recognisable and usable by the system. If the software is useless without the peripheral, it’s considered a driver.

Note that repo has special naming rules.