Moved `java-libkiwix` to new Maven repo.

[MohitMaliFtechiz]

Fixes #62 Fixes #64

• We are moving our java-libkiwix to the new maven repo org.kiwix with version code 1.0.0.
• Updated README.md file to use updated badge. Currently, it will show as "not found" (https://img.shields.io/maven-central/v/org.kiwix/libkiwix) because we have not yet published the artifact on Maven. Once we publish the artifact on Maven, it will start displaying correctly in the badge.
• Previously, we were utilizing libkiwix 12.0.0 and libzim 8.2.0. Now we are preparing to upload java-libkiwix on maven and new versions are available for these libraries. Hence, we're upgrading to libkiwix 12.1.0 and libzim 8.2.1.

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (74c4aba) 92.38% compared to head (197777d) 92.38%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #63 +/- ## ========================================= Coverage 92.38% 92.38% Complexity 213 213 ========================================= Files 44 44 Lines 289 289 Branches 3 3 ========================================= Hits 267 267 Misses 19 19 Partials 3 3 ```

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