OakRun Explorer GUI improvements

[basix-86]

Hi,

I've been using the OakRun Explorer tool and have encountered some difficulties finding and filtering node results for useful information (e.g., node type). The current text format presents too much information, making it cumbersome to navigate.

Based on these observations, I've made the following improvements to the tool:

• Added a search field that highlights all words matching the search key.
• Formatted node information using simple HTML to replace plain text.
• Included links in the HTML to open tar files directly with the Tar File Info tool.
• Replaced the Nimbus L&F with the more modern FlatLaf L&F.

I would appreciate your feedback on these changes. Additionally, I'm interested in contributing to this tool for the project. Please let me know how I can get involved.

Best regards, Marco

[mbaedke]

@basix-86 Great! Re getting involved: First step would be to create a Jira account (https://issues.apache.org/jira), if you don't already have one. Then you can create a new issue there and link this PR to it (no changes to the codebase without a Jira issue).