Suggestion: expose/export component functions

Hi all! I'm relatively new reading and learning about Brighterscript language, and I like a lot this idea!

One thing I found when exposing functions is that sometimes I forgot to declare the <function> tag in the XML file, I know there is a runtime warning when you try to call a non-existent function in a node using callFunc, but I consider that could be a great idea to unify this in Brighterscript code, I think in something like this:

expose function sayHello (name as string) as string
    return "Hello, my name is " + string
end function

Reserved word can be expose or export, I like expose, but maybe someone has a better argument for using export.

That's it!

No files, tests, or entry points are named. Start by reviewing how BrighterScript currently declares functions and maps XML tags, then resolve whether expose or export is appropriate and define the syntax and compiler/runtime behavior before implementation; done means functions can be exposed from BrighterScript without a separate XML declaration.