Added Nested HTML Lists with example (#22537)
Added Nested HTML Lists with example (#22537)

* Added Nested HTML Lists with example

* added `html` markdown for code block, added output example

FreeCodeCamp/FreeCodeCamp,jonathanihm/freeCodeCamp,BhaveshSGupta/FreeCodeCamp,jonathanihm/freeCodeCamp,FreeCodeCamp/FreeCodeCamp,BhaveshSGupta/FreeCodeCamp,BhaveshSGupta/FreeCodeCamp,raisedadead/FreeCodeCamp,raisedadead/FreeCodeCamp