Start 'Street Explorer' test browser for viewing tests

CONTRIBUTING.md

@@ -0,0 +1,13 @@
+# Working on osm2streets
+
+Come hang out at https://github.com/a-b-street/osm2streets to ask questions and improve these docs.
+
+## Pre-requisites
+- rust beta
+- 
+
+## Tests
+
+See the `tests` crate [(docs)](tests/README.md) for a collection of interesting example scenarios.
+
+See `streets-web` crate [(docs)](streets-web/README.md) for a *Street Explorer* test browsing interface.

src/lib.rs

@@ -1,4 +1,4 @@
-mod units;
+pub mod units;
 
 mod road_parts;
 

src/units.rs

@@ -74,6 +74,13 @@ pub enum DrivingSide {
 }
 
 impl DrivingSide {
+    pub fn opposite(&self) -> Self {
+        match self {
+            Self::LHT => Self::RHT,
+            Self::RHT => Self::LHT,
+        }
+    }
+
     pub fn get_direction(&self, side: Side) -> Direction {
         match (self, side) {
             (Self::LHT, Side::Left) | (Self::RHT, Side::Right) => Direction::Forward,

streets-web/.gitignore

@@ -0,0 +1 @@
+dist/*