Fix install script to detect Alpine and suggest installing via npm/yarn

[jsjoeio]

As a user running Alpine, the install script should exit and tell me to install using npm/yarn per the docs.

Related:

• Cannot run on Alpine on WSL2 #3413
• Support for 32-bit Alpine Linux / iSH on iOS? #2261
• npm install -g code-server Alpine Linux #2139

[jsjoeio]

Strangely after testing on Alpine 3.12 (iSH app on iPadOS), it works as expected.

RPReplay_Final1625181106.MP4

After chatting with @code-asher, it turns out if you're using 64 bit Alpine, it tries to install the standalone and fails