[Feature Request] Add Type Checking

[jafaircl]

Feature description:

Add a type checker. Most other CEL implementations have one.

Problem it solves or use case:

A type checker can be useful to determine the output type of the expression without actually evaluating it. For example, checking that an expression evaluates to a boolean before using it as a data filter. Or checking that the output type is what is expected before evaluating compute-heavy expressions.

Proposed implementation or solution:

Adding a type checker should be fairly straightforward. The ground work for environments already exists. It would just take time to actually implement the solution. But, there is plenty of prior art to go off of.

Contribution:

I would be willing to implement the feature myself if there is not the bandwidth to do it otherwise.

Examples or references:

See:
google/cel-go

google/cel-java

projectnessie/cel-java

My own typescript implementation:
@bearclaw/cel

Additional context:

N/A