fix(deno): update types for deno ^1.4.0 (#100)

In version 1.4 Deno adopted;

- the tsconfig setting [importsNotUsedAsValues](https://www.typescriptlang.org/tsconfig#importsNotUsedAsValues) - denoland/deno#7413

This requires the use of;
- type only imports for values which are only used as types (`importsNotUsedAsValues`)

deno.ts

@@ -1,5 +1,5 @@
 import { y18n as _y18n } from './build/lib/index.js'
-import { Y18NOpts } from './build/lib/index.d.ts'
+import type { Y18NOpts } from './build/lib/index.d.ts'
 import shim from './lib/platform-shims/deno.ts'
 
 const y18n = (opts: Y18NOpts) => {