Enable auto-completion in Agda layer

layers/+lang/agda/config.el

@@ -16,3 +16,4 @@ Emacs. If `use-helper', the `agda-mode' executable is used to
 find its location.")
 
 (spacemacs|define-jump-handlers agda2-mode agda2-goto-definition-keyboard)
+(spacemacs|defvar-company-backends agda2-mode)

layers/+lang/agda/packages.el

@@ -11,8 +11,13 @@
 
 (setq agda-packages
       '((agda :location local)
+        company
         golden-ratio))
 
+(defun agda/post-init-company ()
+  (spacemacs|add-company-hook agda2-mode)
+  (push 'company-capf company-backends-agda2-mode))
+
 (defun agda/init-agda ()
   (if (and (eq 'use-helper agda-mode-path)
            (not (executable-find "agda-mode")))