Add prysm.sh script

[prestonvanloon]

This script can be used to download the latest Prysm releases on github.

linux_amd64	linux_arm64	darwin_amd64	windows_amd64
✔️ Confirmed works	✔️ Confirmed works	✔️ Confirmed works	❓ Not tested yet

Example:

./prysm.sh beacon-chain
Latest Prysm version is v0.3.3.
Downloading beacon chain@v0.3.3 to /home/preston/git/prysm/dist/beacon-chain-v0.3.3-linux-amd64 (automatically selected latest available version)
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   622  100   622    0     0   2320      0 --:--:-- --:--:-- --:--:--  2312
100 39.6M  100 39.6M    0     0  13.6M      0  0:00:02  0:00:02 --:--:-- 20.4M
Downloading validator@v0.3.3 to /home/preston/git/prysm/dist/validator-v0.3.3-linux-amd64 (automatically selected latest available version)
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   619  100   619    0     0   1484      0 --:--:-- --:--:-- --:--:--  1484
100 32.5M  100 32.5M    0     0  12.6M      0  0:00:02  0:00:02 --:--:-- 21.7M
Starting Prysm beacon-chain 
...

[garyschulteog]

works on ubuntu/arm64 👍

[rauljordan]

Confirmed works darwin