Add 'rojo doc' command

src/cli/doc.rs

@@ -0,0 +1,26 @@
+use opener::{open, OpenError};
+use snafu::Snafu;
+
+#[derive(Debug, Snafu)]
+pub struct DocError(Error);
+
+#[derive(Debug, Snafu)]
+enum Error {
+    Open { source: OpenError },
+}
+
+impl From<OpenError> for Error {
+    fn from(source: OpenError) -> Self {
+        Error::Open { source }
+    }
+}
+
+pub fn doc() -> Result<(), DocError> {
+    doc_inner()?;
+    Ok(())
+}
+
+fn doc_inner() -> Result<(), Error> {
+    open("https://rojo.space/docs")?;
+    Ok(())
+}