Add decodeEvents function

[qperrot]

Usage related changes

• Implementation of decodeEvents function, which return an array of objects, containing the data of all emitted events.
• Check the branch to see the test [starknet-hardhat-example] (add decode events test starknet-hardhat-example#68)

Development related changes

Checklist:

• Formatted the code
• No linter errors
• Tried to avoid introducing linter warnings
• Performed a self-review of the code
• Rebased to the last commit of the target branch (or merged it into my branch)
• Documented the changes
• Updated the test directory
• Created a PR to the plugin branch of starknet-hardhat-example:
  • Modified test.sh to use my example repo branch
  • Restored test.sh to to use the original branch (after the example repo PR has been merged)
• All tests are passing

[FabijanC]

In the checklist, you said you modified the test directory, but I don't see any changes to it. Your example repo test never got executed because you didn't introduce a test case for it here, in the plugin repo (remember your last PR and how there has to be a check.sh script).