feat: Add EpubFileLoader for EPUB file processing

[danik-tro]

Add EpubFileLoader for EPUB file processing.

Solves #160

Changes

• Implemented a new loader type, EpubFileLoader, in rig-core/src/loaders/epub.rs under the epub feature.
• Added an optional dependency on epub-rs for handling EPUB files.
• Extracts chapters from the EPUB file. Currently, the text is retrieved in XML format, as EPUB files are archives of XML files.
• Potential enhancement: Add methods to EpubFileLoader for stripping XML tags to produce plain text.

[0xMochan]

Great work on this, will be reviewing this soon! I love how you added a by_chapter method which matches by_page. Let me know how creating a custom Loader was, I think there are ways to make it cleaner with loader traits but the way the types are setup might seem a bit confusing at first!

[danik-tro]

Great work on this, will be reviewing this soon! I love how you added a by_chapter method which matches by_page. Let me know how creating a custom Loader was,

Thank you for the feedback! I spent some time understanding how the loader works, and that took the most effort. Compared to researching the existing ones, implementing the new loader took significantly less time. I really like the concept of the type state pattern.

I think there are ways to make it cleaner with loader traits but the way the types are setup might seem a bit confusing at first!

Yes, it does look confusing, but it’s effective at the same time. I’m experimenting with a few improvement options, and if something works out, I’ll share an example.

[0xMochan]

Great work on this, will be reviewing this soon! I love how you added a by_chapter method which matches by_page. Let me know how creating a custom Loader was,

Thank you for the feedback! I spent some time understanding how the loader works, and that took the most effort. Compared to researching the existing ones, implementing the new loader took significantly less time. I really like the concept of the type state pattern.

I think there are ways to make it cleaner with loader traits but the way the types are setup might seem a bit confusing at first!

Yes, it does look confusing, but it’s effective at the same time. I’m experimenting with a few improvement options, and if something works out, I’ll share an example.

Hey, wanted to check up on this. Were you going to introduce anything extra here or is this ready for review? It does look like you need to rebase to main to ensure that this can be merged w/o conflicts. When resolved, you can mark me for review!

[danik-tro]

Great work on this, will be reviewing this soon! I love how you added a by_chapter method which matches by_page. Let me know how creating a custom Loader was,

Thank you for the feedback! I spent some time understanding how the loader works, and that took the most effort. Compared to researching the existing ones, implementing the new loader took significantly less time. I really like the concept of the type state pattern.

I think there are ways to make it cleaner with loader traits but the way the types are setup might seem a bit confusing at first!

Yes, it does look confusing, but it’s effective at the same time. I’m experimenting with a few improvement options, and if something works out, I’ll share an example.

Hey, wanted to check up on this. Were you going to introduce anything extra here or is this ready for review? It does look like you need to rebase to main to ensure that this can be merged w/o conflicts. When resolved, you can mark me for review!

Hi! I've resolved conflicts using the GitHub tool. Let me know if rebase is mandatory; I'll squash commits locally and push them to the branch. The PR is ready to be reviewed. No additional changes aren't going to be added for now, maybe in the next PRs.

[0xMochan]

@danik-tro Could this PR be rebased / merged w/ main! thanks!