Add FAQ to readme (#34)

* Add FAQ to readme

* Add formatting to FAQ

* Fix codestyle issues in readme

* Update README.md

Co-authored-by: Andrey Sitnik <andrey@sitnik.ru>

* Update README.md

Co-authored-by: Andrey Sitnik <andrey@sitnik.ru>

* Update README.md

Co-authored-by: Andrey Sitnik <andrey@sitnik.ru>

---------

Co-authored-by: Andrey Sitnik <andrey@sitnik.ru>

README.md

@@ -125,3 +125,20 @@ You can test only specific files by:
 $ npx check-dts **/*.tsx?
 $ npx check-dts **/*.ts !**/index.ts
 ```
+
+## FAQ
+
+### It seems that check-dts ignores all d.ts-files. How can I fix this?
+
+Please make sure that your tsconfig.json doesn’t include `skipLibCheck: true`.
+Becuase with this [option](https://www.typescriptlang.org/tsconfig#skipLibCheck)
+all `d.ts`-files will be ignored.
+
+### Can I use check-dts as a simple validator for d.ts-files?
+
+Yes you can. But note if you have the typescript in your project
+you can validate whether `d.ts`-files have some issues with the following command:
+
+```sh
+$ npx tsc path/to/your/dts/files/**/*.d.ts --noEmit
+```