Fixed an issue where the SPM package doesn't compile with Xcode 11.4

[akmarinov]

After updating to Xcode 11.4, my project is showing the following issue with RxBluetoothKit:

xcodebuild: error: Could not resolve package dependencies:
   target at '/Users/xcode/Library/Developer/Xcode/DerivedData/project-btxgpemzyyretjcousmtwoebmywz/SourcePackages/checkouts/RxBluetoothKit' contains mixed language source files; feature not supported

I've been able to track down the error to the Info.plist file in the Sources folder.

For whatever reason, Xcode 11.4 now doesn't like that there's a file that's now a .swift one. (Xcode 11.3.1 still works fine)

I've included that file in the excluded section in the package description, which solves the issue.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

Andrew Marinov seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}