Add Swift Package Manager installation instructions for iOS

### Is there an existing issue for this?

- [x] I have searched the existing issues

### What feature should be added?

Mobile SDK supports SPM, we should add that in the installation instructions for iOS. There are only cocoapods instruction right now.

### What is the expected behavior?

Include the SMP installation instructions.

### How will this feature improve the user experience?

Use will get the detailed instruction how to install mobile sdk via SMP.

### What would a solution for this issue look like?

_No response_

Start with the existing iOS installation instructions and find the current CocoaPods section. Add the corresponding Swift Package Manager installation steps, then verify that the iOS documentation clearly explains how to install the Mobile SDK through both methods.

Written by the indexing model from the issue text.