NotificationsScreen: Create API Client

[takahirom]

Add KtorNotificationApi that use a real API endpoint

Reference

• https://github.com/DroidKaigi/droidkaigi-feed-reader-app/blob/c4b9f2a7b76d89ab98de[…]monMain/kotlin/io/github/droidkaigi/feeder/data/KtorStaffApi.kt

[RyuNen344]

API definitions are here

• https://droidkaigi.stoplight.io/docs/ssot-api/b3A6MjQzMzYzOTI-get-announcements-by-language
• https://droidkaigi.stoplight.io/docs/ssot-api/b3A6MjQzMzYzOTM-get-announcements-by-announcement-id

[yurihondo]

@takahirom

Add KtorNotificationApi that use a real API endpoint

I've already add that in #15 . In this Issue, I will try to make sure the API works and modify it if necessary.