feat(fig): add plugin for Fig (#10432)

plugins/fig/README.md

@@ -0,0 +1,9 @@
+# Fig plugin
+
+This plugin sets up completion for [Fig](https://fig.io/).
+
+To use it, add `fig` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... fig)
+```