Align with new Jakarta Namepace

[hantsy]

I think the next major version(3.0???) should consider aligning with the new Jakarta namespace since Jakarta EE 9 and new features from Java ecosystem.

• use jakarta.* to replace the javax.* in the Servlet import.
• Java 17+ or 21+(I like this option)
• New features from JVM and java ecosystem, eg. Reactive Streams, Virtual thread, record, etc.

[gilbertoca]

@hantsy I'm working to stabilize the code source after #10 and #28 .
And I'm following the jakarta discussion in Velocity-Engine project (https://github.com/apache/velocity-engine) as well.