Add version to opam file

Author: lpw25

opam

@@ -1,5 +1,6 @@
 opam-version: "1.2"
 name: "octavius"
+version: "0.1.0"
 maintainer: "[email protected]"
 authors: [ "Leo White <[email protected]>" ]
 homepage: "https://github.com/ocaml-doc/octavius"
@@ -17,4 +18,4 @@ depends: [
 
 build: [[
   "ocaml" "pkg/pkg.ml" "build"
-          "--pinned" "%{pinned}%" ]]
+          "--pinned" "%{pinned}%" ]]