Add one-liner installation command

[jonaprieto]

Let's improve the Juvix user experience by providing a single command for the main installation while including clear instructions for any further steps required to set up dependencies, for which calling juvix doctor can come in handy. This will make the overall process more efficient and user-friendly.

Examples:

• https://github.com/wasmerio/wasmer-install
• https://www.rust-lang.org/tools/install

[paulcadman]

As part of this we could consider bundling the architecture independent wasi-sysroot files into the Juvix compiler binary. We would write the wasi-sysroot to the .juvix-build directory as we do for other artefacts. This would avoid the "set the WASI_SYSROOT" environment setup in the installation.

[jonaprieto]

The script is living in this repo:

• https://github.com/anoma/juvix-installer/