adding rust install

[augustweinbren]

Added installation instruction for rust from their site.
This is needed to create .cargo directory.

[mbsantiago]

Hi @augustweinbren! Huge thanks for the PR. Sorry for asking a possibly simple question, but I'm not sure where the .cargo directory is needed, could you explain please?

[augustweinbren]

It's down here

[mbsantiago]

hehe you are absolutely right! I thought the uv installer would create the directory if it didn't exist, but did you run into this issue when installing it?

[mbsantiago]

I'm not really sure why I included the line source $HOME/.cargo/env, it does not seem to be needed. We could remove it and avoid the rustup installation to keep the setup lean. What do you think? Many thanks again for pointing to this issue!

[augustweinbren]

Looks like uv is a rust-based Python packaging software, so it seems to make sense to have it?

[mbsantiago]

Good point! It seems that uv is shipped as a pre-built binary (for most platforms) so we don't need the rust toolchain for compilation. Sorry for being so hesitant, just thinking about avoiding including additional installation/setup steps if not strictly necessary. I'll try to install acoupi on an RPi without the source $HOME/.cargo/env line to see if installation works.