feat: create an required variable so we can declare our own variable to help with repetitive lambda

[VikralAIT]

Description

Create a way to store lambda as variable so we can create an variable that help with repetitive lamba, example i want to create a brick that will create a page and its cubit, so rather that having to do {{name.pascalCase()}}Cubit everytime we want to mention cubit we could just write {{cubit}} which will show ExampleCubit

[VikralAIT]

never mind i just realize you could do in pre gen without needed to declare it on brick.yaml first
context.vars['cubit'] = '${name.toString().toPascalCase()}Cubit';