add monodocs redirect banner (flyteorg#452)

Signed-off-by: Niels Bantilan <[email protected]>

docs/source/conf.py

@@ -93,15 +93,24 @@
 html_logo = "flyte_circle_gradient_1_4x4.png"
 html_favicon = "flyte_circle_gradient_1_4x4.png"
 
+announcement = """
+📢 This is the old documentation for Flyte.
+Please visit the new documentation <a href="https://docs.flyte.org">here</a>.
+"""
+
 html_theme_options = {
     "light_css_variables": {
         "color-brand-primary": "#4300c9",
         "color-brand-content": "#4300c9",
+        "color-announcement-background": "#FEE7B8",
+        "color-announcement-text": "#535353",
     },
     "dark_css_variables": {
         "color-brand-primary": "#9D68E4",
         "color-brand-content": "#9D68E4",
+        "color-announcement-background": "#493100",
     },
+    "announcement": announcement,
 }
 
 html_context = {