Include instructions for installing with home manager

[zimeg]

Summary

This PR adds a section to the installation instructions for installing the current version of wd with home manager. Tested this with my own setup and it seems to be working well!

Notes

The rev and sha256 fields are tied to a specific release tag and might need updating with new releases. Or it could just be reference for the format. Using the latest tag with an incorrect hash will error with the correct hash displayed, so it's not too bad to figure out the new hash.

But a more formal approach might use `nix-prefetch` to find the actual hash for the version.

$ nix-prefetch-git https://github.com/mfaerevaag/wd v0.5.2
...
{
  "url": "https://github.com/mfaerevaag/wd",
  "rev": "a3ee1ec68ef172d7f8e8f48266ea680c801217b9",
  "date": "2022-10-06T18:18:47+01:00",
  "path": "/nix/store/hjda1gwzxiz3i1axcnwwj71swkvj9kfw-wd",
  "sha256": "063nl0x6y75bsnalppyy69y121fsnv8nfykb8bdl4dd13am7a8p3",
  "hash": "sha256-4yJ1qhqhNULbQmt6Z9G22gURfDLe30uV1ascbzqgdhg=",
  "fetchLFS": false,
  "fetchSubmodules": false,
  "deepClone": false,
  "leaveDotGit": false
}

If this section is wanted in the README.md I'm happy to also add documentation for bumping these values elsewhere!

Reference

• Documentation for the home manager zsh options is listed here
• The repository for nix-prefetch can be found here

[alpha-tango-kilo]

I've never got around to trying NixOS; is needing to use nix-prefetch fairly common for things that don't have formal nix packages? If it's quite common for users to have to do, in my opinion it's fine to leave more minimal instructions, and let the more advanced users sort themselves out, focussing on helping the newbies along

[zimeg]

@alpha-tango-kilo Thanks for reviewing this! I've been diving into Nix as a package manager recently and it's been quite pleasant. Configurations are too much fun to mess with...

My understanding is that nix-prefetch helps find hash values for a specific package without needing to compute the hash yourself or face errors on the first attempt with an incorrect hash. Not super sure if using nix-prefetch is the common approach, but adding packages or plugins by URL and hash seems standard for projects that don't have a nix package.

I totally agree that more minimal instructions are fine too since the error is pretty helpful when the hash is wrong:

error: hash mismatch in fixed-output derivation '/nix/store/pykbkq771vmgjg9iksdssax0b90bp2ix-source.drv':
         specified: sha256-3yJ1qhqhNULbQmt6Z9G22gURfDLe30uV1ascbzqgdhg=
            got:    sha256-4yJ1qhqhNULbQmt6Z9G22gURfDLe30uV1ascbzqgdhg=

[alpha-tango-kilo]

Cheers for explaining further! Happy to merge this as-is based on what you've said :) Thanks for the PRs

[zimeg]

@alpha-tango-kilo And thank you for maintaining this wonderful tool! I'm a big fan!