Closes #733

Replacing:
net.sourceforge.maven-taglib:maven-taglib-plugin:2.4
with
io.github.weblegacy:taglib-maven-plugin:2.6

taglib-maven-plugin

To verify:

]$ git clone https://github.com/jeremiahjstacey/esapi-java-legacy-dev.git ./PR-taglib-docs
]$ cd PR-taglib-docs
]$ mvn site:site
# Alternatively, use your preferred browser to open the index.html file generated from site
]$ firefox target/site/index.html &

1. Three new taglib headings are listed
2. Each tab is selectable
3. When selected, each tab renders unique content about the taglib context for the project.

Expected index.html Display