Charts - more examples

[dlabrecq]

• Created a gnatt-like example, demonstrating an alert timeline using horizontal bar charts
• Updated a pie chart example to demonstrate how to apply custom styles
• Also fixed an issue with undesired space between tick labels and the bottom positioned legend

Closes https://github.com/patternfly/patternfly-react/issues/10844

[patternfly-build]

Preview: https://patternfly-react-pr-10845.surge.sh

A11y report: https://patternfly-react-pr-10845-a11y.surge.sh

[tlabaj]

Can you target v6 branch for these cahnges?