Fix typos with codespell

Using codespell 2.2-dev from current git.

Added `misc/scripts/codespell.sh` to make it easier to run it once in a
while and update the skip and ignore lists.

(cherry picked from commit 1bdb82c64e)

editor/editor_inspector.cpp

@@ -1709,7 +1709,7 @@ void EditorInspector::update_tree() {
 						if (F->get().label != String()) {
 							ep->set_label(F->get().label);
 						} else {
-							//use existin one
+							//use existing one
 							ep->set_label(name);
 						}
 						for (int i = 0; i < F->get().properties.size(); i++) {