soroban-cli: promote all install methods in docs

[leighmcculloch]

The soroban-cli is installable via a few mechanisms now:

• cargo install from source
• cargo bininstall from precompiled binary
• brew install via the stellar/homebrew-tap
• release binaries on github.com/stellar/soroban-tools

As far as I can tell we don't promote any of these installation methods other than the first in the soroban-docs or elsewhere.

[willemneal]

I say we push binstall as it helps install easily in CI and is cross-platform.

[stellarsaur]

We could mention all installation methods in the GitHub README and Soroban Docs, but recommend cargo install and cargo bininstall for the reasons @willemneal mentioned

[leighmcculloch]

Bininstall is helpful, but less so to developers who aren't Rust devs or advanced devs. For rust devs cargo install and cargo bininstall fall on the same plane of convenience, and some will prefer one or the other. Promoting install methods needs to be focused on supporting all users wherever they're at, and brew install helps mac users, and ideally we add other install methods in the future like scoop for windows users, etc.

So I don't think we specifically need to push one install path over the other, but just surface them all.

[janewang]

PR to close stellar/stellar-docs#733