Add version api endpoint (#66)

server/src/main/kotlin/ir/armor/tachidesk/impl/Version.kt

@@ -0,0 +1,6 @@
+package ir.armor.tachidesk.impl
+import ir.armor.tachidesk.BuildConfig
+
+fun getVersion(): String {
+    return BuildConfig.VERSION
+}

server/src/main/kotlin/ir/armor/tachidesk/server/JavalinSetup.kt

@@ -33,6 +33,7 @@ import ir.armor.tachidesk.impl.Source.getSourceList
 import ir.armor.tachidesk.impl.backup.BackupFlags
 import ir.armor.tachidesk.impl.backup.legacy.LegacyBackupExport.createLegacyBackup
 import ir.armor.tachidesk.impl.backup.legacy.LegacyBackupImport.restoreLegacyBackup
+import ir.armor.tachidesk.impl.getVersion
 import ir.armor.tachidesk.server.util.openInBrowser
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -297,6 +298,11 @@ object JavalinSetup {
             ctx.status(200)
         }
 
+        // returns version of the app
+        app.get("/api/v1/version/") { ctx ->
+            ctx.json(getVersion())
+        }
+
         // category modification
         app.patch("/api/v1/category/:categoryId") { ctx ->
             val categoryId = ctx.pathParam("categoryId").toInt()