Add warnings to readme

readme.md

@@ -3,6 +3,8 @@ The c3sign Website
 
 This `git` repository contains the `c3sign.de` website.
 
+Warning: This repository contains more than 1 GB data when cloned.
+
 
 Static content
 --------------
@@ -25,6 +27,11 @@ http://localhost:1313/
 ```
 to view the page.
 
+Warning: Due to the massive amount of images, the *first* Hugo run takes a very
+long time (in the order of 20 - 40 minutes depending on your machine). Subsequent
+runs are much faster (about 1 - 2 seconds) as long as the cache (`resources/_gen/`,
+about 800 MB) is not removed.
+
 
 Build
 -----
@@ -35,3 +42,5 @@ rm -rf public/
 hugo --minify
 ```
 to get a fresh static build in `public/`.
+
+Warning: The build output `public/` is currently about 1.2 GB large.