Initial Swift API for PEM format

[csjones]

📑 Addresses #421

[what-the-diff]

PR Summary

• Addition of SwiftLint configurations

A new file .swiftlint.yml was added, which contains rules and settings for how Swift code within our project should be formatted. It also includes a list of files that should be excluded from the SwiftLint checking process.

• New Files Addition

Several new files have been added to enhance the functionality of our application. These files include functionalities like processing and encoding certificate related data, handling cryptographic operations, converting dates, and returning personalized error messages.

• Expansion of Private Key and Public Key Functionality

Changes have been made to the Asymmetric.swift file. We now have new ways to generate private and public keys from different data representations in the secp256k1 cryptography algorithm.

• Enhanced Error Handling

Errors related to the secp256k1 cryptography algorithm are now categorized in the new CryptoKitErrors.swift file, and more classifications of errors have been added to the existing Errors.swift file.

• Updates to Test Cases

An update was made to the secp256k1Tests.swift file. This has improved a test case allowing it to handle more complex scenarios by validating larger size arrays.