impov: Fix smart-assembly-scaffold (also used for dApp) installation guide

[BringIt-On]

improvement: fixed problems with the smart-assembly-scaffold installation guide that stopped users from getting their local development environment working.

[MysteryPoo]

Should the user see this after those steps?

If so, let's add this in.
If not, let's show what should be seen.

I also think we should address the error:
Error: script failed: vm.envUint: environment variable "ITEM_IN" not found
When running mock-data

[MysteryPoo]

The following should be added to the steps in the README for Smart-Assembly-Scaffold

• Add a step to run mock-data prior to opening the dapp (or better, make note that the dapp won't be able to find the SSU until mock-data is ran)
• Fix the ITEM_IN_ID and ITEM_OUT_ID to be ITEM_IN and ITEM_OUT so that mock-data can run successfully.
• Make a note to change the environment in the DAPP to be Anvil and connect the wallet there.