feat(installer): add windows installer script

[supleed2]

Description of change

Adds Powershell script, following steps as in bash install script, closes #1496.

Install command added to readme will work once shuttle-hq/www#220 is merged.

How has this been tested? (if applicable)

Tested locally on multiple machines, including commenting out codepaths to check both sides of branches. The section for downloading a binary may need to be updated in the future if CI is updated to produce aarch64 windows binaries.

[jonaro00]

Looks good. Will test on my windows machine later

[jonaro00]

Tried it on a machine that has tar but not rust:

• Script assumes Home.cargo\bin exists, and fails if it doesn't (which is not a blocker; we can add checking for sufficient rust install to both scripts later)

(added the bin folder manually, then)

• The exit call after successful install made my powershell window close itself, which is probably not desired. (is it due to not running in a subshell anymore?)

(opened and ran it again)

• The raw download route fails if the destination file already exists. It should overwrite an existing destiantion.

• Other caveat: Only if on non-AMD64 and with no tar.exe does it offer to install rust 🤔 . As said above, we will probably revisit this for both scripts so that the rust check+install can be the first step for both.

[supleed2]

1. Maybe the binary download section can go before cargo.exe install cargo-shuttle --locked inside the cargo.exe check, since this would indicate cargo_home should exist?

Should the script create the bin folder in cargo_home if it doesn't exist?

2. Yes, running in the same shell means it exits, 2 options, prompt user to press enter before exiting, or nest the code in if-else branches and remove all exit calls?

3. I can just add -Force to the Move-Item call?

[jonaro00]

1. Not sure what you mean by that. The binary download is higher prio than cargo install. I don't think we should create "our own" cargo bin folder, but instead let the check (in later PR) for that cargo is installed guard against this error.
2. Hmm, ok. I guess that is due to iex not spawning a sub-process for evaluating it. Maybe it is possible to wrap it in a function and use Return instead? This isn't a major blocker, so it can be left to fix in an upcoming PR.
3. Sounds good.

After resolving (3), this is probably ready to be merged.

[supleed2]

Added the -Force flag and wrapped it in a function, it also restores the $ErrorActionPreference since it no longer exits.

[oddgrd]

Awesome, thanks so much @supleed2!