db.mysql: improve documentation for support on FreeBSD (#26334)

Author: lcheylus

vlib/db/mysql/README.md

@@ -24,6 +24,8 @@ Use `docker container rm some-mysql` to remove it completely, after it is stoppe
 
 For Linux, you need to install `MySQL development` package and `pkg-config`.
 
+For FreeBSD, you need to install the `mariadb118-client` package.
+
 For OpenBSD, you need to install the `mariadb-client` package.
 
 For Windows, install [the installer](https://dev.mysql.com/downloads/installer/) ,

vlib/db/mysql/_cdefs_nix.c.v

@@ -10,6 +10,8 @@ $if $pkgconfig('mysqlclient') {
 	#pkgconfig mariadb
 	$if openbsd {
 		#include <mysql.h> # Please install the mariadb-client package for development headers
+	} $else $if freebsd {
+		#include <mysql.h> # Please install the mariadb118-client package for development headers
 	} $else {
 		#include <mysql.h> # Please install the libmariadb-dev development headers
 	}