lang/org: add lookup handlers for src blocks

- Fixes: `set-lookup-handlers!` couldn't define :definition or
  :references handlers in text-mode derivatives.
- Adds: support for evaluating code in jupyter blocks (#2477).

modules/tools/lookup/config.el

@@ -41,7 +41,8 @@ Used by `+lookup/online'.")
   "Function to use to open search urls.")
 
 (defvar +lookup-definition-functions
-  '(+lookup-xref-definitions-backend-fn
+  '(+lookup-dictionary-definition-backend-fn
+    +lookup-xref-definitions-backend-fn
     +lookup-dumb-jump-backend-fn
     +lookup-project-search-backend-fn
     +lookup-evil-goto-definition-backend-fn)
@@ -73,7 +74,8 @@ argument: the identifier at point. See `set-lookup-handlers!' about adding to
 this list.")
 
 (defvar +lookup-references-functions
-  '(+lookup-xref-references-backend-fn
+  '(+lookup-thesaurus-definition-backend-fn
+    +lookup-xref-references-backend-fn
     +lookup-project-search-backend-fn)
   "Functions for `+lookup/references' to try, before resorting to `dumb-jump'.
 Stops at the first function to return non-nil or change the current
@@ -203,11 +205,5 @@ Dictionary.app behind the scenes to get definitions.")
                  collect (cons service #'+eval-display-results-in-popup))))
 
 
-(when (featurep! +dictionary)
-  (define-key! text-mode-map
-    [remap +lookup/definition] #'+lookup/dictionary-definition
-    [remap +lookup/references] #'+lookup/synonyms))
-
-
 ;;;###package synosaurus
 (setq synosaurus-choose-method 'default) ; use ivy/helm instead of ido