add flipper-plugin keyword to package.json

Summary: For plugins to be discoverable through NPM, they need to have `flipper-plugin` as a keyword. This adds this keyword to all existing plugins (although they are currently not distributed via NPM) and the webside/docs.

Reviewed By: passy

Differential Revision: D17395079

fbshipit-source-id: e42dd31ca39c3754cf729052ee783687748bafe8

src/chrome/PluginInstaller.tsx

@@ -111,7 +111,6 @@ export default function(props: {onHide: () => any}) {
         </SearchBox>
       </Toolbar>
       <ManagedTable_immutable
-        key="FuryEvents"
         rowLineHeight={28}
         floating={false}
         multiline={true}