Add parking=street_side (#73)

Adds a preset for street-side parking¹.

1: https://wiki.openstreetmap.org/wiki/Proposed_features/parking%3Dstreet_side

data/fields/parking/orientation.json

@@ -0,0 +1,12 @@
+{
+    "key": "parking:orientation",
+    "type": "combo",
+    "label": "Orientation",
+    "strings": {
+        "options": {
+            "parallel": "Parallel to the Carriage Way",
+            "diagonal": "Diagonal in Relation to the Carriage Way",
+            "perpendicular": "Meets the Carriage Way at a Straight Angle"
+        }
+    }
+}