doc: add FOUC caveat

Author: somus

README.md

@@ -210,6 +210,13 @@ Also, `target-path` supports [ejs](https://github.com/mde/ejs) and the following
 #### Blueprint files
 Blueprints are basically [ejs](https://github.com/mde/ejs) templates which are rendered with the same three variables(`name`, optional `parent` and `helpers` object) as above.
 
+### Caveats
+
+#### FOUC (Flash of Unstyled Content)
+To make the hot reloading of CSS work, we are not extracting CSS in development. Ideally, during server rendering, we will be extracting CSS, and we will get a .css file, and we can use it in the html template. That's what we are doing in production.
+
+In development, after all scripts get loaded, react loads the CSS as BLOBs. That's why there is a second of FOUC in development.
+
 ## Roadmap
 
 The roadmap discussion thread for v2.0.0 can be found [here](https://github.com/Hashnode/mern-starter/issues/146).