refactor: Move ui.Theme.from_brand() Sass code into an .scss file (#1792)

Author: gadenbuie

examples/brand/app.py

@@ -1,4 +1,3 @@
-import os
 from pathlib import Path
 
 import matplotlib.pyplot as plt
@@ -7,10 +6,8 @@
 from shiny import App, render, ui
 from shiny.ui._theme_brand import bootstrap_colors
 
-# TODO: Move this into the test that runs this app
-os.environ["SHINY_BRAND_YML_RAISE_UNMAPPED"] = "true"
 theme = ui.Theme.from_brand(__file__)
-# theme = ui.Theme()
+# theme = ui.Theme()  ## default theme
 theme.add_rules((Path(__file__).parent / "_colors.scss").read_text())
 
 app_ui = ui.page_navbar(