Expose env via flipperLib

Summary:
This change exposes the env variables via the FlipperLib interface used by plugins.

The variables are already white-listed and safe to be used by plugins according to documentation.

Reviewed By: antonk52

Differential Revision: D40852147

fbshipit-source-id: bbb3b052d33bf5cf75c81166af2400fe6a359256

desktop/flipper-frontend-core/src/flipperLibImplementation/index.tsx

@@ -45,6 +45,7 @@ export function baseFlipperLibImplementation(
     },
     environmentInfo: {
       os: renderHost.serverConfig.environmentInfo.os,
+      env: renderHost.serverConfig.env,
     },
     intern: {
       graphGet: (...args) =>