refactor!(tree-sitter): add +tree-sitter flag

BREAKING CHANGE: break the global nature of the tree sitter
module by adding a +tree-sitter flag to every applicable module

In the background this hooks turn-on-tree-sitter-mode
to the major-mode-hook of the language.
This may also solve the eager loading of tree sitter

modules/lang/agda/config.el

@@ -38,3 +38,8 @@
           "h"   #'agda2-display-implicit-arguments
           "q"   #'agda2-quit
           "r"   #'agda2-restart)))
+
+;; Tree Sitter
+(eval-when! (featurep! +tree-sitter)
+  (add-hook! '(agda-mode
+               agda2-mode) #'turn-on-tree-sitter-mode))