support createPaste

Summary:
Added support for `createPaste` in Sandy plugins

Nice minimalistic example of how to expose a Flipper api to Sandy.

Note that some indirection could be removed by having an interface that is shared directly between `BasePluginClient` and `FlipperLib` (e.g. `PublicFlipperLib`). In contrast to `addMenuEntries` from the previous diff, `createPaste` is basically exposed verbatim to Sandy without additional wrapping, so those cases could be made simpler. Maybe will do that later.

Reviewed By: passy

Differential Revision: D22815873

fbshipit-source-id: e6d0773a35341edfe5de0898317eaadf88de79d0

desktop/app/src/utils/flipperLibImplementation.tsx

@@ -10,6 +10,7 @@
 import type {FlipperLib} from 'flipper-plugin';
 import type {Logger} from '../fb-interfaces/Logger';
 import type {Store} from '../reducers';
+import createPaste from '../fb-stubs/createPaste';
 
 let flipperLibInstance: FlipperLib | undefined;
 
@@ -23,6 +24,7 @@ export function initializeFlipperLibImplementation(
     enableMenuEntries(entries) {
       addSandyPluginEntries(entries);
     },
+    createPaste,
   };
 }