feat(docs): add release version docs show

Author: lijunru-hub

docs/_static/js/generic_version.js

@@ -0,0 +1,8 @@
+var DOCUMENTATION_VERSIONS = {
+    DEFAULTS: { has_targets: false,
+              },
+    VERSIONS: [
+      { name: "latest", old:false},
+      { name: "release-v2.0", old:false},
+    ],
+};

docs/conf_common.py

@@ -36,6 +36,8 @@
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ['../_static']
 
+versions_url = './_static/js/generic_version.js'
+
 # Extra options required by sphinx_idf_theme
 project_slug = 'esp-iot-solution'