Add PlantUML examples

README.md

+# Create Diagrams from Textual Descriptions
+In this GitLab instance you can create diagrams from textual descriptions.
+Therefore, a tool called [Kroki](https://kroki.io) is provided.
+
+This document provides you with a set of examples that can be used to create
+diagrams.
+
+## PlantUML
+
+### Sequence Diagram
+
+```plantuml
+@startuml
+participant User
+
+User -> A: DoWork
+activate A
+
+A -> B: << createRequest >>
+activate B
+
+B -> C: DoWork
+activate C
+C --> B: WorkDone
+destroy C
+
+B --> A: RequestCreated
+deactivate B
+
+A -> User: Done
+deactivate A
+@enduml
+```
+
+### Gantt Diagram
+```plantuml
+@startgantt
+printscale weekly
+
+Project starts the 1st of July 2021
+[Literature Review] lasts 4 weeks
+[Literature Review] is 100% completed
+then [Run Experiments] lasts 12 weeks
+[Run Experiments] is 70% completed
+-- Phase Two --
+then [Data Analysis] lasts 8 weeks
+[Data Analysis] is 0% completed
+then [Write Publication] lasts 6 weeks
+[Write Publication] is 0% completed
+@endgantt
+```
+
+### Display JSON Data
+```plantuml
+@startjson
+{
+  "firstName": "John",
+  "lastName": "Smith",
+  "age": 28,
+  "address": {
+    "streetAddress": "Bautzner Landstr. 400",
+    "city": "Dresden",
+    "state": "Saxony",
+    "postalCode": "01328"
+  },
+  "offices": [
+    {
+      "building": 512,
+      "room": 1234
+    },
+    {
+      "building": 312,
+      "room": 3
+    }
+  ],
+  "departments": []
+}
+@endjson
+```
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