docs: create readme

.github/workflows/build.yml

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 name: CI
 
 on:
+  push:
+    branches:
+      - main
   workflow_dispatch:
 
 jobs:

.github/workflows/test.yml

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 name: Test
 
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+  push:
+    branches:
+      - main
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README.md

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-# release_schedule
+# Release Schedule
 
-A new Flutter project.
+A small app using the Wikidata API to show upcoming movies.
 
-## Getting Started
+You can try out the live web version at [daniel-michel.github.io/release_schedule](https://daniel-michel.github.io/release_schedule).
 
-This project is a starting point for a Flutter application.
+Android and Linux builds can be found in the latest build run: [](https://github.com/daniel-michel/release_schedule/actions/workflows/build.yml) 
 
-A few resources to get you started if this is your first Flutter project:
+Currently, only a simple list of upcoming movies is shown:
+![](screenshots/movie_list.png)
 
-- [Lab: Write your first Flutter app](https://docs.flutter.dev/get-started/codelab)
+The floating button at the bottom right can be used to load the upcoming movies and the button at the top right to clear the movies that where already loaded.
-- [Cookbook: Useful Flutter samples](https://docs.flutter.dev/cookbook)
 
-For help getting started with Flutter development, view the
+
-[online documentation](https://docs.flutter.dev/), which offers tutorials,
+## Wikidata API
-samples, guidance on mobile development, and a full API reference.
+
+The Implementation can be found at [./lib/api/wikidata_movie_api.dart](./lib/api/wikidata_movie_api.dart).
+
+To get information about the upcoming movies multiple APIs are used.
+
+First the SPARQL API is used to retrieve upcoming movies using the endpoint "https://query.wikidata.org/sparql" with the following query:
+```sql
+SELECT
+  ?movie
+  ?movieLabel
+  (MIN(?releaseDate) as ?minReleaseDate)
+WHERE {
+  ?movie wdt:P31 wd:Q11424;         # Q11424 is the item for "film"
+         wdt:P577 ?releaseDate;      # P577 is the "publication date" property
+         wdt:P1476 ?title.
+  FILTER (xsd:date(?releaseDate) >= xsd:date("$date"^^xsd:dateTime))
+
+  SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
+}
+GROUP BY ?movie ?movieLabel
+ORDER BY ?minReleaseDate
+LIMIT $limit
+```
+Where `$limit` is the maximum number of movies that are retrieved and `$date` the starting date from which movies are retrieved.
+`$limit` is currently set to 100 and `$date` one week before the current one.
+However, because there are multiple publication dates for most movies, the retrieved movies just need to have one publication date that is on or after `$date` for the movie to be included in the result. The `minReleaseDate` is not necessarily the release date displayed in the App, therefore some movies in the App might show up as having been released a long time ago.
+
+To get additional information about the movies and all release dates (in case some are before `$date` and some after) the API endpoint "https://www.wikidata.org/w/api.php?action=wbgetentities" is used.