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/stack/0020-valid-parentheses.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0020. Valid Parentheses][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src

org/cpp/dsa/stack/0084-largest-rectangle-in-histogram.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0084. Largest Rectangle In Histogram][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src

org/cpp/dsa/stack/0150-evaluate-reverse-polish-notation.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0150. Evaluate Reverse Polish Notation][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src

org/cpp/dsa/stack/0155-min-stack.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0155. Min Stack][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src

org/cpp/dsa/stack/0682-baseball-game.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0682. Baseball Game][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src

org/cpp/dsa/stack/0726-number-of-atoms.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0726. Number of Atoms][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src

org/cpp/dsa/stack/0739-daily-temperatures.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0739. Daily Temperatures][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src

org/cpp/dsa/stack/0853-car-fleet.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0853. Car Fleet][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src

org/cpp/dsa/stack/0901-online-stock-span.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0901. Online Stock Span][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src

org/cpp/dsa/stack/1544-make-the-string-great.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*1544. Make The String Great][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src