v3.18.5

• Increases minimum version for the IMA SDK for iOS to iOS 14.
• Fixes a bug where user context wasn't passed with stream error.
• Enables Same App Key for apps that also bundle GMA version 9.14.0 and above.
• Adds the IMAVideoStitcherLiveStreamRequest class, which provides support for the Google Video Stitcher Live API.
• Public beta release of Google Video Stitcher API.
• Public beta release of Secure Signals API.