Stop checking in generated .d.ts; keep only public API snapshots (#1801)

Summary:
Pull Request resolved: #1801

Makes the per-package TypeScript definition files (`packages/*/types/*.d.ts`) build artefacts instead of checked-in source, now that `microsoft/api-extractor` gives us snapshots of public APIs.

Note - `.d.ts` files are still emitted for every module at build time and published to npm.

The main benefit of this is to reduce developer friction - previously, any change to a module's API would require rebuilding TS definitions. Now, a manual step is only required when changing the *public* API, which is both much less common and should always be done intentionally.

Changelog: Internal

Reviewed By: huntie

Differential Revision: D112750746

fbshipit-source-id: a0563d5f1fa43f5604be905a5c9fa5a6bcfad43d

Author: robhogan

.gitignore

@@ -5,6 +5,9 @@
 /reports
 npm-debug.log*
 packages/*/build/
+# Generated TypeScript definitions. Build artifacts produced on demand from
+# Flow sources (for npm publish and public API snapshotting); not checked in.
+packages/*/types/
 
 website/build/
 website/i18n/*

package.json

@@ -48,7 +48,7 @@
   },
   "scripts": {
     "build-clean": "rm -rf ./packages/*/build",
-    "build": "node ./scripts/build.js",
+    "build": "yarn run build-ts-defs && node ./scripts/build.js",
     "build-ts-defs": "node -r @babel/register ./scripts/generateTypeScriptDefinitions.js",
     "build-api-snapshots": "node -r @babel/register ./scripts/generateApiSnapshots.js",
     "verify-api-snapshots": "node -r @babel/register ./scripts/generateApiSnapshots.js --verify",
@@ -62,7 +62,7 @@
     "test-coverage": "yarn run build && yarn run jest --coverage -i && node scripts/mapCoverage.js",
     "test-smoke": "yarn start build --config packages/metro/src/integration_tests/metro.config.js TestBundle.js --out /tmp/TestBundle",
     "typecheck": "flow check",
-    "typecheck-ts": "tsc --project tsconfig.json",
+    "typecheck-ts": "yarn run build-ts-defs && tsc --project tsconfig.json",
     "update-babel-flow-lib-defs": "node -r @babel/register ./scripts/updateBabelFlowLibraryDefinitions",
     "update-version": "node ./scripts/updateVersion"
   },