Add version switcher in documentation

Author: paulromano

doc/source/_static/switcher.json

@@ -0,0 +1,10 @@
+[
+    {
+        "name": "dev",
+        "version": "latest"
+    },
+    {
+        "name": "0.1.0",
+        "version": "v0.1.0"
+    }
+]

doc/source/conf.py

@@ -52,6 +52,9 @@
     'astropy': ('https://docs.astropy.org/en/stable/', None)
 }
 
+import watts
+version = release = watts.__version__
+
 # -- Options for HTML output -------------------------------------------------
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
@@ -65,16 +68,15 @@
 
 html_theme = 'pydata_sphinx_theme'
 
-html_theme_options = {
-    'github_url': 'https://github.com/watts-dev/watts',
-}
-
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ['_static']
+
 html_logo = '_static/watts.svg'
+
 html_theme_options = {
+    "github_url": "https://github.com/watts-dev/watts",
     "favicons": [
         {
             "rel": "icon",
@@ -86,5 +88,11 @@
             "sizes": "32x32",
             "href": "watts_32x32.png",
         },
-    ]
+    ],
+    "switcher": {
+        "json_url": "https://watts.readthedocs.io/en/latest/_static/switcher.json",
+        "url_template": "https://watts.readthedocs.io/en/{version}/",
+        "version_match": version if '-dev' not in version else 'dev',
+    },
+    "navbar_end": ["version-switcher", "navbar-icon-links"]
 }