feat(docs): move getAllowance.sol smart contract example from wiki to wasp

[vivekjain23]

Description of change

This is the PR addressing moving Wiki contracts to the wasp repo. A GetAllowance.sol contract was added, alongside a solo test for it.

Type of change

fixes issue: #1613

How the change has been tested

A Solo test.

Make sure to provide instructions for the maintainer as well as any relevant configurations.

Change checklist

Tick the boxes that are relevant to your changes, and delete any items that are not.

• [X] I have followed the contribution guidelines for this project
• [X] I have performed a self-review of my own code
• [X] I have selected the develop branch as the target branch
• [X] I have commented my code, particularly in hard-to-understand areas
• [X] I have made corresponding changes to the documentation
• [X] I have added tests that prove my fix is effective or that my feature works
• [X] I have checked that new and existing unit tests pass locally with my changes

[vivekjain23]

isc.allow()

To make the test more meaningful, I think a call to isc.allow() is to be made before getAllowanceFrom, Then check if they are equal.

Yes, you are right. I have tried finding the isc.allow() or similar methods, but I was unable to find them. Please guide me regarding the same if possible.

[salaheldinsoliman]

isc.allow()

To make the test more meaningful, I think a call to isc.allow() is to be made before getAllowanceFrom, Then check if they are equal.

Yes, you are right. I have tried finding the isc.allow() or similar methods, but I was unable to find them. Please guide me regarding the same if possible.

You can create a separate function in the contract, then call isc.allow() before getAllowanceFrom(). Here is an example: https://wiki.iota.org/isc/how-tos/core-contracts/basics/allowance/allow/

[lucas-tortora]

could you rename the PR to follow the guidelines on confluence?