Description not fully fleshed out for Google-Code-in-2019 and good first task (not tagging as such yet) just yet
Extensions such as Page-Previews have json such as the below for various documentation
"config": { "@PopupsVirtualPageViews": "@var bool: Whether the extension should log virtual pageviews.", "PopupsVirtualPageViews": false },
This is no longer needed in manifest_version: 2 as you can do
"config": { "PopupsVirtualPageViews": { "description": "@var bool: Whether the extension should log virtual pageviews.", "value": false } },
Depending on what is in the extension.json file, it may need further updates
CI may inform you of further modifications that are needed