MAINT: Add pipeline tags to readme

README.md

 # caosdb-julialib
 
+[![pipeline
+status](https://gitlab.indiscale.com/caosdb/src/caosdb-julialib/badges/main/pipeline.svg)](https://gitlab.indiscale.com/caosdb/src/caosdb-julialib/-/commits/main)
+[![coverage report](https://gitlab.indiscale.com/caosdb/src/caosdb-julialib/badges/main/coverage.svg)](https://gitlab.indiscale.com/caosdb/src/caosdb-julialib/-/commits/main)
+[![documentation (placeholder)](https://img.shields.io/badge/docs-latest-blue.svg)](https://docs.indiscale.com/caosdb-julialib/)
+
 ## Welcome
 
 This is the development repository of **caosdb-julialib** - a Julia