feat: Add decorators - Githubissues

Fixes #

Changelog Entry

(Experimental) Added initial decorators support, in PR #5205, by @OEvgeny
- Introduced internal botframework-webchat-api/decorator import, in PR #5205, by @OEvgeny
- Added DecoratorComposer and ActivityDecorator to be used for decorating activity border, in PR #5205, by @OEvgeny

This adds a way to decorate various things in WebChat in the future. For now it supports activity decoration with a custom border.

The design introduces decorators to WebChat. The current implementation includes support for activity decoration with custom border decorator.

Key components of the design:

ActivityBorderDecoratorMiddleware: Middleware stack for managing activity border changes
ActivityDecorator: A React component for decorating activities e.g. inside of the WebChat or activity middlewares
DecoratorComposer: Allows multiple decorators to be passed together and initialized according to the type of decorator
createDecoratorComposer: A factory function for creating decorator composer
ActivityDecoratorRequestType: Describes activity decorator request

Users provide an array of middleware functions to DecoratorComposer
The DecoratorComposer initializes these functions based on the decorators type
When, for example, an activity is rendered, it passes the activity to the ActivityDecorator to form a request and process middlewars, which apply the appropriate changes

This section is for contributors to review your work.

[x] ~Accessibility reviewed (tab order, content readability, alt text, color contrast)~
[x] Browser and platform compatibilities reviewed
[x] CSS styles reviewed (minimal rules, no z-index)
[x] ~Documents reviewed (docs, samples, live demo)~
[x] ~Internationalization reviewed (strings, unit formatting)~
[x] package.json and package-lock.json reviewed
[x] ~Security reviewed (no data URIs, check for nonce leak)~
[x] Tests reviewed (coverage, legitimacy)