Add types and properties to support the feature of math solvers on the web, which are dynamically generated pages based on user input.

SolveMathAction (parent type: Action): The action that takes in a math expression and directs users to a page potentially capable of solving/simplifying that expression.

MathSolver (parent type: LearningResource): A math solver which is capable of solving a subset of mathematical problems.

mathExpression (expected type: Text): The query string that can be injected into the target property of the SolveMathAction.