chore: add ci badge

Author: w1am

README.md

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 # KurrentDB Java Client
 
+[![CI](https://github.com/kurrent-io/KurrentDB-Client-Java/actions/workflows/pull-requests.yml/badge.svg)](https://github.com/kurrent-io/KurrentDB-Client-Java/actions/workflows/pull-requests.yml)
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 KurrentDB is the event-native database, where business events are immutably stored and streamed. Designed for event-sourced, event-driven, and microservices architectures.
 
 This repository contains an [KurrentDB][kurrent] Client SDK written in Java for use with languages on the JVM. It is