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/two-pointers/0011-container-with-most-water.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0011. Container With Most Water][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/two-pointers/0015-3sum.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0015. 3Sum][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/two-pointers/0042-trapping-rain-water.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0042. Trapping Rain Water][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/two-pointers/0125-valid-palindrome.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0125. Valid Palindrome][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/two-pointers/0167-two-sum-ii-input-array-is-sorted.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0167. Two Sum II Input Array Is Sorted][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/two-pointers/0259-3sum-smaller.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0259. 3Sum Smaller][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/two-pointers/0344-reverse-string.org

@@ -3,6 +3,15 @@
 :NEETCODE: [[../../../../leetcode/out/roadmap.org::*0344. Reverse String][Roadmap]]
 :END:
 
+** TODO Approach
+Write your approach here.
+
+** TODO Python
+#+begin_src python
+
+#+end_src
+
+** TODO C++
 #+begin_src cpp
 
 #+end_src