add scoop in downloads section of github and possibly remove portableapps

[t3dium]

As its a better way of installing portable apps and is already listed on scoop's main repos: scoop install freetube

While they should be safe, download at your own risk

it should also be 100% safe as it simply fetches the download from your github repository which can be verified using scoop cat

[efb4f5ff-1298-471a-8973-3d47447115dc]

Opened #2553. Portableapps will not be removed because we want to give the users of FT all the options there are.