generate manuals in markdown

[pmlopes]

The vertx toolchain processes manuals written in asciidoc. This project already has a simple codetrans plugin to convert the examples from java to javascript, however the final result is still an asciidoc file.

The problem arises when we try to use these files in the website, as the website uses vuepress and doesn't support asciidoc.

We need a solution to either convert the asciidoc to markdown in a reliable way, or update/enhance vuepress to load the asciidoc files during the build as a preprocess step and feeding some markdown transformation.