Expose Typescript types in libSquoosh (#1142)

* Expose type declarations in libSquoosh npm package

* Add comment on why we remove the tsbuildinfo

* Fix PreprocessOptions type

Resize should require at least one of the width, height.
The other options are optional for all preprocessors

* Update libSquoosh README to reflect encode changes

I also removed requiring `await image.decoded` call before calling
preprocess or encode since they decode the image before the operation

libsquoosh/lib/move-d-ts.js

@@ -0,0 +1,26 @@
+const fs = require('fs');
+const del = require('del');
+const path = require('path');
+
+const tsOutputDir = path.resolve('..', '.tmp', 'ts', 'libsquoosh');
+const tsOutputSourceDir = path.join(tsOutputDir, 'src');
+const buildDir = path.resolve('build');
+
+(async () => {
+  await del(path.join(buildDir, '*.d.ts'));
+  const files = await fs.promises.readdir(tsOutputSourceDir);
+
+  const movePromises = [];
+  for (const file of files) {
+    if (file.endsWith('d.ts') || file.endsWith('d.ts.map')) {
+      movePromises.push(
+        fs.promises.rename(
+          path.join(tsOutputSourceDir, file),
+          path.join(buildDir, file),
+        ),
+      );
+    }
+  }
+  // We need to remove `tsconfig.tsbuildinfo` otherwise TS does not emit unchanged `.d.ts` files
+  await del([path.join(tsOutputDir, 'tsconfig.tsbuildinfo')], { force: true });
+})();