✨ Add pnpm completions (#692)

Hi!
I added `pnpm` completions. There are a lot of commands, but I added the
most used ones (at least from me)

see you around!

custom-completions/pnpm/pnpm-completions.nu

@@ -0,0 +1,74 @@
+
+export def "nu-complete get scripts" [] {
+  open package.json 
+  | get scripts
+  #| describe record<start: string, build: string, test: string, eject: string>
+  | transpose # to convert the record<start: string, build: string, test: string, eject: string> into a table
+  | rename value description
+}
+
+export def "nu-complete get deps" [] {
+  let packagejson = (open ./package.json)
+  let deps = try { $packagejson | get dependencies | columns } catch { [] }
+  let devDeps = try { $packagejson | get devDependencies | columns } catch { [] }
+
+  $deps | append $devDeps
+}
+
+def "nu-complete pnpm" [] {
+  [
+   # manage your dependencies section
+   { value: "add", description: "Installs a package and any packages that it depends on. By default, any new package is installed as a prod dependency" } 
+   { value: "import", description: "Generates a pnpm-lock.yaml from an npm package-lock.json (or npm-shrinkwrap.json) file" } 
+   { value: "install", description: "(i) Install all dependencies for a project" } 
+   { value: "install-test", description: "(it) Runs a pnpm install followed immediately by a pnpm test" } 
+   { value: "link", description: "(ln) Connect the local project to another one" } 
+   { value: "prune", description: "Removes extraneous packages" } 
+   { value: "rebuild", description: "(rb) Rebuild a package" } 
+   { value: "remove", description: "(rm) Removes packages from node_modules and from the project's package.json" } 
+   { value: "unlink", description: "Unlinks a package. Like yarn unlink but pnpm re-installs the dependency after removing the external link" } 
+   { value: "update", description: "(up) Updates packages to their latest version based on the specified range" } 
+   # review your dependencies section
+   { value: "audit", description: "Checks for known security issues with the installed packages" } 
+   { value: "licenses", description: "Check licenses in consumed packages" } 
+   { value: "list", description: "(ls) Print all the versions of packages that are installed, as well as their dependencies, in a tree-structure" } 
+   { value: "outdated", description: "Check for outdated packages" } 
+   # run your scripts section
+   { value: "exec", description: "Executes a shell command in scope of a project" } 
+   { value: "run", description: "Runs a defined package script" } 
+   { value: "start", description: "Runs an arbitrary command specified in the package's `start` property of its `scripts` object" } 
+   { value: "test", description: "(t) Runs a package's `test` script, if one was provided" } 
+   # others
+   { value: "pack", description:"" } 
+   { value: "publish", description:"Publishes a package to the registry" } 
+   { value: "root", description:"" } 
+   { value: "store", description:"store add, store path, store prune & store status" } 
+  ]  
+}
+
+export extern "pnpm" [
+  command?: string@"nu-complete pnpm"
+  --recursive(-r)                    # Run the command for each project in the workspace.
+  --help(-h)                         # Print help information
+]
+
+export extern "pnpm run" [
+  command?: string@"nu-complete get scripts"
+  --help(-h)                         # Print help information
+]
+
+export extern "pnpm remove" [
+  command?: string@"nu-complete get deps"
+  --help(-h)                         # Print help information
+]
+
+export extern "pnpm add" [
+  --help(-h)                         # Print help information
+  --save-exact(-E)                   # Install exact version
+  --global(-g)                       # Install as a global package
+  --recursive(-r)                    #  Run installation recursively in every package found in subdirectories or in every workspace package, when executed inside a workspace. For options that may be used with `-r`, see "pnpm help recursive"
+  --save-dev(-D)                     # Save package to your `devDependencies`
+  --save-optional(-O)                #  Save package to your `optionalDependencies`
+  --save-peer                        #  Save package to your `peerDependencies` and `devDependencies`
+  --save-prod(-P)                    #  Save package to your `dependencies`. The default behavior
+]