Leverage github actions for tests and linting.
This includes fixing a bunch of issues highlighted by golangci
including:
* Dead code.
* Ineffectual assigns.
* Goto warnings.
* Nil return err.
* Reused literal strings.
* Test parameter order.
Also:
* Setup clog.
This change adds a handful of functions to `otto.Otto` type that make
it easier to create proper `Error` values from native code. Previously,
the only way to do this was to call the error's constructor from
JavaScript like `vm.Call("TypeError", "message")`. `Call` can fail for
various reasons, and also modifies the current call stack.
These new functions can't fail, and since they don't involve any
JavaScript execution, won't modify the call stack. The new functions
are:
* `MakeCustomError(name, message string) Value`
* `MakeRangeError(message string) Value`
* `MakeSyntaxError(message string) Value`
* `MakeTypeError(message string) Value`
`MakeCustomError` creates an `Error` object with a specific `name` value.
The other functions cover some common error types, and call specific
functions in the runtime to construct errors with the correct prototypes.
If we need to implement any other error types, it'll mostly be copy/paste.
