message: Reduce type noise
diff: @@ -18,6 +18,7 @@ import { JsonValue } from '@backstage/config';
  import * as os from 'os';
  import { resolve as resolvePath } from 'path';
  import { createIncludeTransform } from './include';
  +import { TransformFunc } from './types';
  const root = os.platform() === 'win32' ? 'C:\\' : '/';
  const substituteMe = '${MY_SUBSTITUTION}';
  @@ -29,18 +30,7 @@ const env = jest.fn(async (name: string) => {
  } as { [name: string]: string })[name];
  });
  -const substitute = async (
  - value: JsonValue,
  -): Promise<
  - | {
  - applied: false;
  - }
  - | {
  - applied: true;
  - value: JsonValue | undefined;
  - newBaseDir?: string | undefined;
  - }
  -> => {
  +const substitute: TransformFunc = async value => {
  if (typeof value !== 'string') {
  return { applied: false };
  }
  