[iOS] MaterialComponents dependency clash

Environment
Provide version numbers for the following components (information can be retrieved by running tns info in your project folder or by inspecting the package.json of the project):

• CLI: 6.0.3
• Cross-platform modules: 6.0.6
• Android Runtime: 6.0.1
• iOS Runtime: 6.0.2
• Plugin(s):

Describe the bug

The hardcoded version of the MaterialComponents/Tabs pod restricts the use of other updated components such as MaterialComponents/ProgressView. It results in an error when installing the pods:

[!] CocoaPods could not find compatible versions for pod "MaterialComponents/ProgressView+Theming":
  In Podfile:
    MaterialComponents/ProgressView+Theming

Specs satisfying the `MaterialComponents/ProgressView+Theming` dependency were found, but they required a higher minimum deployment target.
'pod install' command failed.

To Reproduce

Add a podfile to any project with the following lines:

pod 'MaterialComponents/ProgressView'
pod 'MaterialComponents/ProgressView+Theming'

Expected behavior
App compiles fine with no problems.

Sample project

Additional context

One restriction on the iOS side compared to the Android side is that on Android you are able to set variables to modify the library versions that uses, this is currently not true for the iOS side. Adding this capability may be a better long term solution.