message: [now-cli] Use `entrypoint` instead of `src` for `startDevServer()`
  Otherwise the `src` is modified to not have the file extension when used
  with zero-config API routes.
diff: @@ -1452,7 +1452,7 @@ export default class DevServer {
  const { builder, package: builderPkg } = match.builderWithPkg;
  if (typeof builder.startDevServer === 'function') {
  const devServerResult = await builder.startDevServer({
  - entrypoint: match.src,
  + entrypoint: match.entrypoint,
  workPath: this.cwd,
  });
  if (devServerResult) {
  @@ -1482,7 +1482,7 @@ export default class DevServer {
  false
  );
  } else {
  - debug(`Skipping \`startDevServer()\` for ${match.src}`);
  + debug(`Skipping \`startDevServer()\` for ${match.entrypoint}`);
  }
  }
  