[Enhancement] iOS Apple or Android logos should be displayed on "Get the App" button depending on supported platform

[SoftVision-PaulOiegas]

[Affected versions]:

• Firefox 63.0 and above

[Affected Platforms]:

• All Windows
• All Mac OS
• All Linux

[Prerequisites]:

• Set the "extensions.webapi.testing" boolean pref to "true" in "about:config" page.

[Steps to reproduce]:

1. Open Firefox browser and navigate to https://testpilot.dev.mozaws.net.
2. Observe the Lockbox iOS "Get the App" button from Featured experiment section.
3. Scroll down and click on Notes experiment card.
4. Observe the "Get the App" button for Notes Android app.

[Expected result]:

• "Get the App" button displays the iOS Apple or Android logos depending on experiment platforms supported.

[Actual result]:

• There is no difference between iOS or Android "Get the App" buttons, a mobile phone icon is displayed for both.

[Notes]:

• Here is a screenshot of the issue:

[KhushilMistry]

Hey, I want to work on this issue. Will make a PR soon.
I have a question : Should the color be the same for both the button i.e. green ? Or you want blue for iOS experiment and green for Android experiment ? Something like following :

Experiement Page has different design now.

[SoftVision-PaulOiegas]

hey @KhushilMistry, please don't rush with this since it's an enhancement proposal and wasn't triaged yet. We'll need to see if @johngruen thinks it adds value to the current implementation or not first.