feat(nsc): add completion plugin

plugins/nsc/nsc.plugin.zsh

@@ -0,0 +1,13 @@
+if (( ! $+commands[nsc] )); then
+  return
+fi
+
+# If the completion file doesn't exist yet, we need to autoload it and
+# bind it to `nsc`. Otherwise, compinit will have already done that.
+if [[ ! -f "$ZSH_CACHE_DIR/completions/_nsc" ]]; then
+  typeset -g -A _comps
+  autoload -Uz _nsc
+  _comps[nsc]=_nsc
+fi
+
+nsc completion zsh >| "$ZSH_CACHE_DIR/completions/_nsc" &|