Update CNCF Landscape Summary Table with Envoy details

Hi All,

The CNCF Business Value Subcommittee has developed a project summary table to supplement the CNCF Landscape and include further information about CNCF projects for the wider cloud native community. We would like to request the Envoy project submit a PR to the CNCF Landscape repository with additional details that will help further inform the community about your project and its use cases through the popular landscape and this new addition.

The table is located here: https://landscape.cncf.io/summary
There are directions located here: https://github.com/cncf/landscape/blob/master/readme_summary.md

Many thanks for this - we hope it will help further get the word out about your project.

Simon Forster
CNCF Business Value Subcommittee