Redo the keyboard references in the documentation

[sy2002]

Instead of having the following line in our documentation (taken from the main README.md):

Enter M then L there. You should see something like "Memory/Load".

We could have:

Enter M and then L there. You should see something like "Memory/Load".

Also the cursor keys are available: ← ↑ → ↓

And Enter and any other key we like.