add env variables for branch and deployment url

Author: jderochervlk

app/routes/MdxRoute.res

@@ -320,7 +320,7 @@ let default = () => {
               }
             })
           )}
-          editHref={`https://github.com/rescript-lang/rescript-lang.org/blob/master${loaderData.filePath->Option.getOrThrow}`}
+          editHref={`https://github.com/rescript-lang/rescript-lang.org/blob/${Env.github_branch}${loaderData.filePath->Option.getOrThrow}`}
         >
           <div className="markdown-body"> {component()} </div>
         </DocsLayout>

package.json

@@ -76,4 +76,4 @@
     "vite-plugin-devtools-json": "^1.0.0",
     "vite-plugin-env-compatible": "^2.0.1"
   }
-}
+}

src/bindings/Env.res

@@ -0,0 +1,18 @@
+// If Vite if running in dev mode
+external dev: bool = "import.meta.env.DEV"
+
+// Cloudflare deployment URL
+external deployment_url: option<string> = "import.meta.env.DEPLOYMENT_URL"
+
+// The current github branch
+external github_branch: option<string> = "import.meta.env.GITHUB_BRANCH"
+let github_branch = switch github_branch {
+| Some(branch) => branch
+| None => "master"
+}
+
+// the root url of the site, e.g. "https://rescript-lang.org/" or "http://localhost:5173/"
+let root_url = switch deployment_url {
+| Some(url) => url
+| None => dev ? "http://localhost:5173/" : "https://rescript-lang.org/"
+}

src/components/Meta.res

@@ -15,7 +15,7 @@ let make = (
   ~ogImage="/Art-3-rescript-launch.jpg",
   ~version: option<Url.version>=?,
 ) => {
-  let ogImage = "https://rescript-lang.org" ++ ogImage
+  let ogImage = Env.root_url ++ ogImage
 
   let title = switch title {
   | None