doc/check-certificates: update notifications

doc/check-certificates.d/notification-01-warn.avif
----- >8 -----
[rsc] 🔏️⚠️ Certificate warning: rsc.eworm.de

A certificate on rsc is about to expire.

Name:           rsc.eworm.de
CommonName:     rsc.eworm.de
SubjectAltNames:
                DNS:rsc.eworm.de
Private key:    available
Fingerprint:    f21bd7e64eef82b963938fecd07ab0210194129d7829ba08c2d212d063f3b07c
Issuer chain:   E7 -> ISRG Root X2
Validity:
    from:       2025-09-09 13:30:10
    to:         2025-12-07 13:30:09
Expires in:     1w 3d 11:37:06
----- >8 -----

doc/check-certificates.d/notification-02-renew.avif
----- >8 -----
[rsc] 🔏️ Certificate renewed: rsc.eworm.de

A certificate on rsc has been renewed.

Name:           rsc.eworm.de
CommonName:     rsc.eworm.de
SubjectAltNames:
                DNS:rsc.eworm.de
Private key:    available
Fingerprint:    f21bd7e64eef82b963938fecd07ab0210194129d7829ba08c2d212d063f3b07c
Issuer chain:   E7 -> ISRG Root X2
Validity:
    from:       2025-11-07 13:30:09
    to:         2026-02-05 13:30:08
Expires in:     11w 3d 02:25:23
----- >8 -----

doc/check-certificates.md

@@ -19,9 +19,10 @@ Description
 This script tries to download and renew certificates, then notifies about
 certificates that are still about to expire.
 
-### Sample notification
+### Sample notifications
 
-![check-certificates notification](check-certificates.d/notification.avif)
+![check-certificates notification warning](check-certificates.d/notification-01-warn.avif)  
+![check-certificates notification renew](check-certificates.d/notification-02-renew.avif)
 
 Requirements and installation
 -----------------------------