Drop support for iOS 12, tvOS 12, macOS 10.15, watch0S < 7, and Xcode 13

[Widcket]

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)

📋 Changes

This PR raises the deployment target of JWTDecode.swift as follows:

• iOS 12.0 -> 13.0
• tvOS 12.0 -> 13.0
• macOS 10.15 -> 11.0
• watchOS 6.2 -> 7.0

Additionally, support for Xcode 13 was dropped, and as such the minimum Swift version was raised to 5.7 (the version shipped with Xcode 14.0).

[userNameIsBoris]

Hi! Just wondering, why did you drop it? It doesn't look like necessary change.

I'm working on the project with iOS 12 deployment target and today i ran into error after package update. Had to fix dependency on 1.0.1.

[Widcket]

Hi @userNameIsBoris, we're aligning our Swift libraries to support iOS 13+, as per our Support Policy.

[userNameIsBoris]

@Widcket Got it, thanks. Have a nice day!