Introduce migrations folder + improve README.md + add custom CDN for Material Icons

migrations/0_6to0_7.py

@@ -0,0 +1,17 @@
+from playhouse.migrate import migrate, SqliteMigrator, MySQLMigrator
+from peewee import MySQLDatabase, SqliteDatabase
+from app import database
+
+if type(database) == MySQLDatabase:
+    migrator = MySQLMigrator(database)
+elif type(database) == SqliteDatabase:
+    migrator = SqliteMigrator(database)
+else:
+    print("Unsupported database")
+    exit()
+
+with database.atomic():
+    migrate(
+        
+    )
+