Scaffold workspaces

![image](https://github.com/facebook/react-forget/assets/1390709/bb27e33f-6a88-4b71-8ce2-aeb8db0372f7) 

This is an attempt to scaffold yarn workspaces into our repo with as minimal as 
possible changes to our current setup and directory structure. Essentially this 
PR moves current `src` into `packages/babel-plugin-react-forget` as a first step 
to keep everything working. Later on when we're ready we can split out a 
`react-compiler` package that is decoupled from Babel, but it's too early for 
that now

compiler/.github/workflows/ci.yml

@@ -17,15 +17,13 @@ jobs:
           cache-dependency-path: forget/yarn.lock
       - run: yarn install --immutable --immutable-cache
         working-directory: forget
-      - run: yarn prettier:ci
+      - run: yarn workspace babel-plugin-react-forget run prettier:ci
         working-directory: forget
-      - run: yarn build
+      - run: yarn workspace babel-plugin-react-forget run build
         working-directory: forget
-      - run: yarn lint
+      - run: yarn workspace babel-plugin-react-forget run lint
         working-directory: forget
-      - run: yarn test
+      - run: yarn workspace babel-plugin-react-forget run test
         working-directory: forget
-      - run: yarn install --immutable --immutable-cache
-        working-directory: forget/packages/snap
-      - run: yarn snap:build && yarn snap
+      - run: yarn workspace babel-plugin-react-forget run snap:build && yarn workspace babel-plugin-react-forget run snap
         working-directory: forget

compiler/.github/workflows/test262.yml

@@ -18,7 +18,7 @@ jobs:
           cache-dependency-path: forget/yarn.lock
       - run: yarn install --immutable --immutable-cache
         working-directory: forget
-      - run: yarn build
+      - run: yarn workspace babel-plugin-react-forget run build
         working-directory: forget
       - id: test262
         name: Run test262