This is another text diagramming tool akin to Mermaid. This does not seem to work with default GitHub markdown parser, but it is available in both GitLab and HackMD.
!define ICONURL https://raw.githubusercontent.com/tupadr3/plantuml-icon-font-sprites/v2.1.0
skinparam defaultTextAlignment center
!include ICONURL/common.puml
!include ICONURL/font-awesome-5/gitlab.puml
!include ICONURL/font-awesome-5/java.puml
!include ICONURL/font-awesome-5/rocket.puml
!include ICONURL/font-awesome/newspaper_o.puml
FA_NEWSPAPER_O(news,good news!,node) #White {
FA5_GITLAB(gitlab,GitLab.com,node) #White
FA5_JAVA(java,PlantUML,node) #White
FA5_ROCKET(rocket,Integrated,node) #White
}
gitlab ..> java
java ..> rocket
@startmindmap
* root node
* some first level node
* second level node
* another second level node
* another first level node
@endmindmap
It may be possible to use with external service.
Doesn't work without some effort (bad URL characters)

Does work (html entity encoding, see https://www.url-encode-decode.com)
Advantage is that the image source stays with the rendered file.
This server can render a remote UML file (both a pro and a con):
I can't tell if this is hosting the content, but the Plant UML isn't really inspectable with this service.