Add option for "alpha mode" with warning and green theme

website/_harp.json

@@ -80,6 +80,7 @@
             }
         ],
 
+        "ALPHA": true,
         "V_CSS": "1.6",
         "V_JS": "1.2",
         "DEFAULT_SYNTAX": "python",

website/_includes/_navigation.jade

@@ -9,6 +9,9 @@ nav.c-nav.u-text.js-nav(class=landing ? "c-nav--theme" : null)
         .u-text-label.u-padding-small.u-hidden-xs=SUBSECTION
 
     ul.c-nav__menu
+        if ALPHA
+            - var NAVIGATION = { "Usage": "/docs/usage", "Reference": "/docs/api" }
+
         each url, item in NAVIGATION
             li.c-nav__menu__item(class=(url == "/") ? "u-hidden-xs" : null)
                 +a(url)=item

website/_includes/_page-docs.jade

@@ -10,6 +10,14 @@ main.o-main.o-main--sidebar.o-main--aside
             if tag
                 +tag=tag
 
+        if ALPHA
+            +infobox("⚠️ You are viewing the spaCy v2.0 alpha docs")
+                |  This page is part of the alpha documentation for spaCy v2.0
+                |  and does not reflect the state of the latest stable release.
+                |  #[+a("#") See here] for more information on how to install
+                |  and test the new version. To read the official docs for
+                |  v1.x, #[+a("https://spacy.io/docs") go here].
+
         !=yield
 
     +grid.o-content.u-text

website/_layout.jade

@@ -35,7 +35,10 @@ html(lang="en")
     link(rel="shortcut icon" href="/assets/img/favicon.ico")
     link(rel="icon" type="image/x-icon" href="/assets/img/favicon.ico")
 
-    if SUBSECTION == "usage"
+    if ALPHA && SECTION == "docs"
+        link(href="/assets/css/style_green.css?v#{V_CSS}" rel="stylesheet")
+
+    else if SUBSECTION == "usage"
         link(href="/assets/css/style_red.css?v#{V_CSS}" rel="stylesheet")
 
     else