Added update feature

app/src/main/java/xyz/quaver/pupil/util/update.kt

@@ -0,0 +1,31 @@
+package xyz.quaver.pupil.util
+
+import kotlinx.serialization.json.*
+import java.net.URL
+
+fun getReleases(url: String) : JsonArray {
+    return URL(url).readText().let {
+        Json(JsonConfiguration.Stable).parse(JsonArray.serializer(), it)
+    }
+}
+
+fun checkUpdate(url: String, currentVersion: String) : JsonObject? {
+    val releases = getReleases(url)
+
+    if (releases.isEmpty())
+        return null
+
+    if (currentVersion != releases[0].jsonObject["tag_name"]?.content)
+        return releases[0].jsonObject
+
+    return null
+}
+
+fun getApkUrl(releases: JsonObject, releaseName: String) : Pair<String?, String?>? {
+    releases["assets"]?.jsonArray?.forEach {
+        if (Regex(releaseName).matches(it.jsonObject["name"]?.content ?: ""))
+            return Pair(it.jsonObject["browser_download_url"]?.content, it.jsonObject["name"]?.content)
+    }
+
+    return null
+}