docs: fix diff link

Author: uhyo

docs/diff.md

@@ -1,18 +1,20 @@
 
 # Diffs
 
-- [es2015.collection.d.ts](es2015.collection.d.ts.md)
-- [es2015.core.d.ts](es2015.core.d.ts.md)
-- [es2015.generator.d.ts](es2015.generator.d.ts.md)
-- [es2015.iterable.d.ts](es2015.iterable.d.ts.md)
-- [es2015.promise.d.ts](es2015.promise.d.ts.md)
-- [es2015.proxy.d.ts](es2015.proxy.d.ts.md)
-- [es2015.reflect.d.ts](es2015.reflect.d.ts.md)
-- [es2017.object.d.ts](es2017.object.d.ts.md)
-- [es2018.asyncgenerator.d.ts](es2018.asyncgenerator.d.ts.md)
-- [es2018.asynciterable.d.ts](es2018.asynciterable.d.ts.md)
-- [es2019.object.d.ts](es2019.object.d.ts.md)
-- [es2021.promise.d.ts](es2021.promise.d.ts.md)
-- [es2021.string.d.ts](es2021.string.d.ts.md)
-- [es2022.object.d.ts](es2022.object.d.ts.md)
-- [es5.d.ts](es5.d.ts.md)
+The following files are improved in better-typescript-lib:
+
+- [es2015.collection.d.ts](./diff/es2015.collection.d.ts.md)
+- [es2015.core.d.ts](./diff/es2015.core.d.ts.md)
+- [es2015.generator.d.ts](./diff/es2015.generator.d.ts.md)
+- [es2015.iterable.d.ts](./diff/es2015.iterable.d.ts.md)
+- [es2015.promise.d.ts](./diff/es2015.promise.d.ts.md)
+- [es2015.proxy.d.ts](./diff/es2015.proxy.d.ts.md)
+- [es2015.reflect.d.ts](./diff/es2015.reflect.d.ts.md)
+- [es2017.object.d.ts](./diff/es2017.object.d.ts.md)
+- [es2018.asyncgenerator.d.ts](./diff/es2018.asyncgenerator.d.ts.md)
+- [es2018.asynciterable.d.ts](./diff/es2018.asynciterable.d.ts.md)
+- [es2019.object.d.ts](./diff/es2019.object.d.ts.md)
+- [es2021.promise.d.ts](./diff/es2021.promise.d.ts.md)
+- [es2021.string.d.ts](./diff/es2021.string.d.ts.md)
+- [es2022.object.d.ts](./diff/es2022.object.d.ts.md)
+- [es5.d.ts](./diff/es5.d.ts.md)