Added the Types of Blockchains section (#24242)
Added the Types of Blockchains section (#24242)

Briefly described permissionless and permissioned blockchains
raisedadead/FreeCodeCamp,BhaveshSGupta/FreeCodeCamp,FreeCodeCamp/FreeCodeCamp,raisedadead/FreeCodeCamp,jonathanihm/freeCodeCamp,BhaveshSGupta/FreeCodeCamp,BhaveshSGupta/FreeCodeCamp,FreeCodeCamp/FreeCodeCamp,jonathanihm/freeCodeCamp