Add TODO checkboxes to Python/C++ sub-headings

- roadmap.org: *** TODO Python and *** TODO C++ with [/] cookie
  on each problem heading for [0/2] progress tracking
- Note files now have TODO Approach, TODO Python, TODO C++
  sections for structured problem solving

org/cpp/dsa/2-d-dynamic-programming/0097-interleaving-string.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0097. Interleaving String][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src