Adds AdaptiveCardsComposer and AdaptiveCardsContext for composability

[compulim]

Changelog Entry

• Adds AdaptiveCardsComposer and AdaptiveCardsContext for composability for Adaptive Cards, by @compulim, in PR #2648

Description

Today, we support UI recomposition, but not with Adaptive Cards. This is because we only expose a minimal <Composer> but not a full version which include Adaptive Cards support.

This PR will add UI composability for activities with Adaptive Cards. This is required for our "Smart Display" sample, which will be submitted later.

Goal: we will add a new <Composer> with enhancements specific for Adaptive Cards.

Specific Changes

• Add internal AdaptiveCardsComposer and AdaptiveCardsContext, which store Adaptive Cards specific content
• When loading a full-bundle
  • Enhance Composer with FullComposer, which enhance by adding Adaptive Cards specific content, and load additional style set dedicated for Adaptive Cards
  • Enhance createStyleSet with createFullStyleSet, which enhance by adding Adaptive Cards specific styles
• Propagate defaultProps and propTypes from minimal Composer and BasicWebChat
• Default renderMarkdown to undefined instead of text => text

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• Testing Added

[tdurnford]

LGTM

[coveralls]

Coverage increased (+0.1%) to 63.679% when pulling d415aa0 on compulim:feat-adaptivecards-context into 5b2e0c2 on microsoft:master.