icu4c seems to be be missing

Author: hummeltech

.github/actions/dependencies/install/action.yml

@@ -77,6 +77,7 @@ inputs:
       curl
       glib
       httpd
+      icu4c
       iniparser
       libmemcached
       mapnik

docs/build/building_on_macos.md

@@ -4,7 +4,7 @@ This document provides users with step-by-step instructions on how to compile an
 
 Please see our [Continuous Integration script](/.github/workflows/build-and-test.yml) for more details.
 
-## macOS 11/12/13/14
+## macOS 11/12/13/14/15
 
 ```shell
 #!/usr/bin/env bash
@@ -22,6 +22,7 @@ brew install \
   curl \
   glib \
   httpd \
+  icu4c \
   iniparser \
   libmemcached \
   mapnik \