feat(stern): introduce stern plugin

plugins/stern/stern.plugin.zsh

@@ -0,0 +1,14 @@
+# Completion
+if (( ! $+commands[stern] )); then
+  return
+fi
+
+# If the completion file doesn't exist yet, we need to autoload it and
+# bind it to `stern`. Otherwise, compinit will have already done that.
+if [[ ! -f "$ZSH_CACHE_DIR/completions/_stern" ]]; then
+  typeset -g -A _comps
+  autoload -Uz _stern
+  _comps[stern]=_stern
+fi
+
+stern --completion zsh >| "$ZSH_CACHE_DIR/completions/_stern" &|