feat: adds support for loading external theme CSS for MFEs (#689)

Author: dcoa

.env.development

@@ -27,4 +27,5 @@ FAVICON_URL=https://edx-cdn.org/v3/default/favicon.ico
 IGNORED_ERROR_REGEX=
 MFE_CONFIG_API_URL=
 APP_ID=
-SUPPORT_URL=https://support.edx.org
+SUPPORT_URL=https://support.edx.org
+PARAGON_THEME_URLS={}

.env.test

@@ -28,3 +28,4 @@ IGNORED_ERROR_REGEX=
 MFE_CONFIG_API_URL=
 APP_ID=
 SUPPORT_URL=https://support.edx.org
+PARAGON_THEME_URLS={}

docs/how_tos/assets/paragon-theme-loader.png

@@ -1,4 +1 @@
-@import "@edx/brand/paragon/fonts";
-@import "@edx/brand/paragon/variables";
-@import "@openedx/paragon/scss/core/core";
-@import "@edx/brand/paragon/overrides";
+@use "@openedx/paragon/styles/css/core/custom-media-breakpoints.css" as paragonCustomMediaBreakpoints;