Add scoop extra README

[ina6ra]

I needed an extra bucket to install with scoop.
I referred to LxRunOffline for how to write README.

• DDoSolitary/LxRunOffline: A full-featured utility for managing Windows Subsystem for Linux (WSL)

[z-Fng]

Hi. @Kyome22

Is there still a chance that future releases will be published on GitHub?

Scoop can no longer detect updates since v2.0.

• Relates to: runcat@2.0: Remove checkver & autoupdate, add arm64 support, fix suggest ScoopInstaller/Extras#16427

[Kyome22]

@z-Fng
For the time being, we plan to distribute only via the Microsoft Store. Because an app without a code-signing certificate may be flagged as a trojan, a certificate is required; however, obtaining and maintaining a code-signing certificate for distribution outside the Microsoft Store is quite costly.

[z-Fng]

Got it. Thank you so much for the reply!