add vorburger.exec & zt-exec

Hello @akullpp and awesome-java maintainers,

would you consider adding https://github.com/vorburger/ch.vorburger.exec ? FYI re. "popularity" of vorburger.exec don't look just at the stars on that repo - it's [used really widely indirectly through MariaDB4j](https://github.com/vorburger/MariaDB4j/).

and even the "competition" to (my) vorburger.exec, the https://github.com/zeroturnaround/zt-exec ? ;-) just FYI see also https://github.com/zeroturnaround/zt-exec/pull/25

FYI I'm the same guy from #465 (and #653) from a while ago.

Thanks for maintaining this!

README.md

@@ -940,6 +940,8 @@ A curated list of awesome Java frameworks, libraries and software.
 - [CRaSH](http://www.crashub.org) - Provides a shell into a JVM that's running CRaSH. Used by Spring Boot and others.
 - [Dex](https://github.com/PatMartin/Dex) - Java/JavaFX tool capable of powerful ETL and data visualization.
 - [Embulk](http://www.embulk.org) - Bulk data loader that helps data transfer between various databases, storages, file formats, and cloud services.
+- [Exec by Vorburger.ch](https://github.com/vorburger/ch.vorburger.exec) - launch external processes, with significant improvements over Apache Commons Exec.
+- [Exec by ZT](https://github.com/zeroturnaround/zt-exec) - another external process utility
 - [fswatch](https://github.com/vorburger/ch.vorburger.fswatch) - Micro library to watch for directory file system changes, simplifying java.nio.file.WatchService
 - [Gephi](https://github.com/gephi/gephi) - Cross-platform for visualizing and manipulating large graph networks.
 - [Guava](https://github.com/google/guava) - Collections, caching, primitives support, concurrency libraries, common annotations, string processing, I/O, and more.