feat(pspdfkit-cordova-android): add plugin

[radazzouz]

⚠️ Note: I opened this pull request for visibility. It is still work in progress. It needs to be tested before reviewing it. ⚠️

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This PR adds PSPDFKit Plugins for Android and iOS.

TODO:

• Make sure that PSPDFKitCordovaiOS works in a newly created Ionic project.
• Make sure that PSPDFKitCordovaAndroid works in a newly created Ionic project

[radazzouz]

I was unsuccessful in running the plugin locally on iOS. I have not attempted to run Android yet.

I did follow the developer instruction here https://github.com/ionic-team/ionic-native/blob/master/DEVELOPER.md and it seems the plugin is not installed. I also did some extensive research (Stack Overflow, this repo, https://ionicframework.com/docs/native/, etc.) to try and find a solution. I may be missing an integration step.

I am attaching the sample project here for future reference.

How to Reproduce:

• Download and unzip the sample project.
• run npm install
• Download PSPDFKit and place PSPDFKit.framework and PSPDFKitUI.framework in platforms/ios
• run ionic cordova run ios

Expected:

The PDF should be presented.

Actual:

Nothing happens.

Additional information:

When I run the workspace from Xcode, I get logs like these:

019-01-11 11:12:52.075611-0500 IonicDemo[4644:1770849] WARN: Ionic Native: tried calling PSPDFKitCordovaIOS.present, but the PSPDFKitCordovaIOS plugin is not installed.
2019-01-11 11:12:52.075969-0500 IonicDemo[4644:1770849] WARN: Install the PSPDFKitCordovaIOS plugin: 'ionic cordova plugin add pspdfkit-cordova-ios'

[radazzouz]

Closing in favor of #3210