MultiReactionBuilder class

Merges multiple ReactionBuilder widgets into one widget tree.

MultiReactionBuilder improves the readability and eliminates the need to nest multiple ReactionBuilders.

By using MultiReactionBuilder we can go from:

ReactionBuilder(
  builder: (context) {},
  child: ReactionBuilder(
    builder: (context) {},
    child: ReactionBuilder(
      builder: (context) {},
      child: ChildA(),
    ),
  ),
)

to:

MultiReactionBuilder(
  builders: [
    ReactionBuilder(
      builder: (context) {},
    ),
    ReactionBuilder(
      builder: (context) {},
    ),
    ReactionBuilder(
      builder: (context) {},
    ),
  ],
  child: ChildA(),
)

MultiReactionBuilder converts the ReactionBuilder list into a tree of nested ReactionBuilder widgets. As a result, the only advantage of using MultiReactionBuilder is improved readability due to the reduction in nesting and boilerplate.