Clarify multiarch support in README.

README.md

@@ -18,6 +18,14 @@ Debian 12 (slim) is used as base image.
 | `go-junit-report` | 2.1.0   | go-junit-report | [External link](https://github.com/jstemmer/go-junit-report) |
 | `delve`           | 1.22.1  | delve           | [External link](https://github.com/go-delve/delve)           |
 
+## Multiarch support
+
+This image contains versions for both amd64 (AMD/Intel CPUs and their clones) and arm64 (Rockchips, Apple Silicon and so on).
+
+Note, that **amd64** image built on my CI server, while **arm64** image I building on my local machine with `built_multiarch.sh`
+for each published tag. It is because I have no separate arm64 machine (yet) and it's emulation on my server's CPU is freaking
+slow (imagine Linux installation is going for three whole hours!).
+
 ## HOME
 
 Home directory is `/home/container`.