Update README badge to display latest version

[Copilot]

The README badge pointed to v8 instead of the current version (v21) and used the generic "Go Reference" label rather than displaying the version number.

Changes:

• Replaced pkg.go.dev reference badge with shields.io version badge that displays the latest GitHub tag
• Badge now shows version number (e.g., v21.2.0) and links to pkg.go.dev versions page
• Normalized URLs to use lowercase repository name for consistency

Before:

[![Go Reference](https://pkg.go.dev/badge/github.com/adyen/adyen-go-api-library/v8.svg)](https://pkg.go.dev/github.com/adyen/adyen-go-api-library/v8)

After:

[![Go Version](https://img.shields.io/github/v/tag/adyen/adyen-go-api-library?label=version)](https://pkg.go.dev/github.com/adyen/adyen-go-api-library/v21?tab=versions)

The badge will automatically update with new releases.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• checkout-test.adyen.com
  • Triggering command: /tmp/go-build2285112514/b001/adyen-go-api-library.test /tmp/go-build2285112514/b001/adyen-go-api-library.test -test.testlogfile=/tmp/go-build2285112514/b001/testlog.txt -test.paniconexit0 -test.timeout=10m0s (dns block)
• img.shields.io
  • Triggering command: /usr/bin/curl curl -s REDACTED (dns block)
• shields.io
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Feature]: Add badge with published version</issue_title>
<issue_description>### Feature summary

In the README add badge with the latest published version from pkg.go, like for example we do for the Java library

[![Maven Central](https://img.shields.io/maven-central/v/com.adyen/adyen-java-api-library)](https://central.sonatype.com/artifact/com.adyen/adyen-java-api-library/)

</issue_description>

<agent_instructions>It looks like there is already a badge on the README, but it is incorrect. It should point to the latest version and display the version number.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [Feature]: Add badge with published version #543

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.