Uupdate js value covnersion

[Sharktheone]

This PR mainly adds another trait IntoRustValue, which can convert JSValues into the correct Rust types. Because of that ValueConversion was renamed to IntoJSValue

This makes it way easier to convert JSValues to Rust values in the macro I want to write. I decided to make a separate PR for that because it doesn't really fit to the macro things.

Secondly, slices and Vecs can be can be converted to a JSArray and back.
JSArray can also be converted to JSValue and Vec<JSValue>

Finally, I removed the `#[allow(X)] macros and fixed the warnings generated by that.

Next Steps

• JS Interop Macro
• Better Way to modify Rust values from JS Functions
• Use V8 Slots for Context
• Reevaluate the need of owned context args