yarnConfigHook: apply as a postConfigure hook

[getchoo]

Description of changes

Split off from #335751

This follows in this example of npmConfigHook and allows for using this
hook alongside others that may override configurePhase

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[philiptaron]

This makes sense.

Result of nixpkgs-review pr 338093 run on x86_64-linux 1

1 package failed to build:

• powerdns-admin

18 packages built:

• auto-changelog
• coc-diagnostic
• codefresh
• diagnostic-languageserver
• dotenv-cli
• get-graphql-schema
• koodo-reader
• listmonk
• postlight-parser
• screego
• spectral-language-server
• textlint-rule-prh
• treedome
• vim-language-server
• vimPlugins.coc-diagnostic
• xplorer
• yarnConfigHook
• your_spotify

powerdns-admin is broken on master.