Example for main docs with markov chain

[jlperla]

As the main example for the docs:

• Below the https://quantecon.github.io/SimpleDifferentialOperators.jl/dev/#Solving-HJBE-with-jump-diffusion-1 add in another example "Solving HJBE with jump diffusions and markov chain" or something like that
• Create the same process as in the Jump diffusion example above, call it L_a or something like that
• Create another process, without the jumps and with a different drift and slightly different payoff function pi, call if L_b
• Reflecting barriers for both (at the same corners, with the same z_bar)
• Create a Q intensity matrix, maybe [-0.01 0.01; 0.02 -0.02]
• Stack the L_a and L_b with Q and then solve for the v. Split into v_a with a @view and v_b. Plot both on the same graph.