README: Install chromium

README.md

@@ -2,6 +2,14 @@
 
 Validata user interface
 
+## Requirements
+
+PDF report uses [Headless Chromium](https://chromium.googlesource.com/chromium/src/+/lkgr/headless/README.md).
+Please install:
+```bash
+apt install -y chromium
+```
+
 ## Install
 
 We recommend using [virtualenv](https://virtualenv.pypa.io/en/stable/).