docs: various #12823

- increase python line-length limit from 88 => 100.
- gen_help_html: fix bug in "tag" case (tbl_count => tbl_contains)

ref #15632
fix #18215
fix #18479
fix #20527
fix #20532

Co-authored-by: Ben Weedon <ben@weedon.email>

src/nvim/hashtab.c

@@ -194,7 +194,7 @@ void hash_debug_results(void)
 #endif  // ifdef HT_DEBUG
 }
 
-/// Add item for key "key" to hashtable "ht".
+/// Add (empty) item for key `key` to hashtable `ht`.
 ///
 /// @param key Pointer to the key for the new item. The key has to be contained
 ///            in the new item (@see hashitem_T). Must not be NULL.