Add missing hiatus, web novel, and mixed media enums

[Katsute]

Prerequisites

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• I have checked that no other similar pull request already exists.
• My code follows the general code style as the rest of the code.
• I have checked that no sensitive information is exposed.
• Build compiles.
• Build passes test cases.

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Changes Made

List any changes made and/or other relevant issues.

• Add missing Manga status OnHiatus
• Add missing Anime source MixedMedia, WebNovel
• Add missing Unknown type
• Rename Anime source Digital_Manga → DigitalManga
• Rename Anime source Web_Manga → WebManga
• Fallback to unknown rather than null

https://github.com/KatsuteDev/Mal4J/actions/runs/2449424775

[Katsute]

@sinon-bot dispatch mal_ci

[ghost]

🚀 Dispatched Workflow

Dispatched workflow mal_ci.yml on branch undocumented@485876c

_{This workflow was dispatched by @Katsute.}

[Katsute]

@sinon-bot dispatch mal_ci

[ghost]

🚀 Dispatched Workflow

Dispatched workflow mal_ci.yml on branch undocumented@485876c

_{This workflow was dispatched by @Katsute.}

[Katsute]

@sinon-bot approve

[ghost]

✔ Pull Approved

_{This pull was approved by @Katsute.}