Add nightly favicon and Binder [ci skip]

website/gatsby-config.js

@@ -17,6 +17,8 @@ const DEFAULT_TEMPLATE = path.resolve('./src/templates/index.js')
 const NIGHTLY_BRANCHES = ['spacy.io-develop']
 
 const isNightly = !!+process.env.SPACY_NIGHTLY || NIGHTLY_BRANCHES.includes(process.env.BRANCH)
+const favicon = isNightly ? `src/images/icon_nightly.png` : `src/images/icon.png`
+const binderBranch = isNightly ? 'nightly' : site.binderBranch
 
 module.exports = {
     siteMetadata: {
@@ -26,6 +28,7 @@ module.exports = {
         ...models,
         universe,
         nightly: isNightly,
+        binderBranch,
     },
 
     plugins: [
@@ -132,7 +135,7 @@ module.exports = {
                 background_color: site.theme,
                 theme_color: site.theme,
                 display: `minimal-ui`,
-                icon: `src/images/icon.png`,
+                icon: favicon,
             },
         },
         {