Updated README with additional instructions for loading ZIM files and articles

[MohitMaliFtechiz]

Fixes #50

Changes made in the README:

• Added a section explaining how to load a ZIM file by creating an Archive object.
• Clarified the description of the mainPage property, detailing its behavior when dealing with redirects and non-existent entries.
• Provided code snippets and instructions for loading articles via title and path, including a reminder to properly decode the URL path before passing it to hasEntryByPath.

These changes aim to improve the documentation and assist developers in effectively utilizing the java-kibkiwix library to work with zim files.

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (4fed04f) 92.38% compared to head (cb3dce7) 92.38%.

:exclamation: Current head cb3dce7 differs from pull request most recent head 190473f. Consider uploading reports for the commit 190473f to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #60 +/- ## ========================================= 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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