dovecot - Feb 2023 - Small suggestion for improvement of pigeonhole/imapsieve documentation

Hello all,

this is my first post on this list and I would like to introduce myself 
briefly. My name is Matthias and I am from Saxony in Germany. I'm 
working with Unix and mail systems for a long time - actually with focus 
for NetBSD and Cyrus IMAP. Occasionally I also use Dovecot, which has 
several reasons. Today, one of the reasons was that I would like to 
trigger Sieve scripts when moving mail within mailbox folders - i.e. at 
an unspecified time after the actual mail arrival. In doing so, I came 
across the imapsieve extension for Pigeonhole fairly quickly and decided 
that the administrative Sieve scripts in imapsieve were exactly what I 
needed. However, despite having debug logging fully up, I couldn't 
figure out until just now why my sieve script wasn't running despite 
having IMAP events logged. Even intentionally defining an invalid script 
did not result in an error, so it seemed to be ignored altogether. Until 
I just now came across that I seem to have misunderstood the documentation.

The template shown for the imapsieve_mailboxXXX_ parameters suggested to 
me that a sequence number of three digits must / can be specified here. 
Thus, I started numbering my parameters with imapsieve_mailbox001.

However, while researching in various forums, I came across only 
examples that use imapsieve_mailbox1_ as the first parameter. In 
desperation I tried this out - now it works for me, too.

Long story short - I don't know if I'm the only one who has made this 
mistake so far. A little hint in the documentation[1] would have helped 
me, how the XXX is meant exactly. I am referring to this section:

```
This setting configures the name of a mailbox for which administrator 
scripts are configured. The `XXX? in this setting is a sequence number, 
which allows configuring multiple associations between Sieve scripts and 
mailboxes. The settings defined hereafter with matching sequence numbers 
apply to the mailbox named by this setting. The sequence of configured 
mailboxes ends at the first missing imapsieve_mailboxXXX_name setting. 
This setting supports wildcards with a syntax compatible with the IMAP 
LIST command, meaning that this setting can apply to multiple or even 
all (?*?) mailboxes.
```

What do you think about adding a small explanatory sentence to the 
documentation? For example:

```
This setting configures the name of a mailbox for which administrator 
scripts are configured. The `XXX? in this setting is a sequence number, 
which allows configuring multiple associations between Sieve scripts and 
mailboxes.

The sequence number must begin with the digit 1 without preceding zeros 
and may have a maximum of three digits.

The settings defined hereafter with matching sequence numbers apply to 
the mailbox named by this setting. The sequence of configured mailboxes 
ends at the first missing imapsieve_mailboxXXX_name setting. This 
setting supports wildcards with a syntax compatible with the IMAP LIST 
command, meaning that this setting can apply to multiple or even all 
(?*?) mailboxes.
```

Many greetings
Matthias


[1] https://doc.dovecot.org/configuration_manual/sieve/plugins/imapsieve/