fix: set capability index (informalsystems#1258)

.changelog/unreleased/bug-fixes/ibc/1257-set-capability-index.md

@@ -0,0 +1,3 @@
+- Set the index of `ibc::ics05_port::capabilities::Capability` ([#1257])
+
+[#1257]: https://github.com/informalsystems/ibc-rs/issues/1257

modules/src/ics05_port/capabilities.rs

@@ -9,10 +9,20 @@ impl Capability {
     pub fn new() -> Capability {
         Self { index: 0x0 }
     }
+
+    pub fn index(&self) -> u64 {
+        self.index
+    }
 }
 
 impl Default for Capability {
     fn default() -> Self {
         Self::new()
     }
 }
+
+impl From<u64> for Capability {
+    fn from(index: u64) -> Self {
+        Self { index }
+    }
+}