Merge #2639

2639: Update demo docs with new capabilities r=mergify[bot] a=Diman0

## What type of PR?

documentation

## What does this PR do?
Update the demo documentation that the demo server now also exposes the new RESTful API.

### Related issue(s)
n/a

## Prerequisites
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [ n/a] In case of feature or enhancement: documentation updated accordingly
- [ /na] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/workflow.html#changelog) entry file.


Co-authored-by: Dimitri Huisman <diman@huisman.xyz>

docs/demo.rst

@@ -16,12 +16,13 @@ If you find actual bugs when using the demo server, please report these!
 Functionality
 -------------
 
-- The server is reset every day at 3am, UTC.
+- The server is reset every day at 3am, 12pm, 8pm UTC.
 - You can send mail from any client to the server.
   However, the SMTP server is made incapable of relaying the e-mail to the destination server.
   As such, the mail will never arrive. This is to prevent abuse of the server.
 - The server is capable of receiving mail for any configured domains.
 - The server exposes IMAP, POP3 and SMTP as usual for connection with mail clients such as Thunderbird.
+- The RESTful API is enabled.
 - The containers have limited (throttled) CPU, this means it can respond slow during heavy operations.
 - The containers have limited memory available and will be killed when exceeded.
   This is to prevent people from doing nasty things to the server as a whole.
@@ -35,6 +36,8 @@ Connecting to the server
  * Admin UI : https://test.mailu.io/admin/
  * Admin login : ``admin@test.mailu.io``
  * Admin password : ``letmein``
+ * RESTful API: https://test.mailu.io/api
+ * API token: ``Bearer APITokenForMailu``
 
 Adding domains
 --------------