Slimeread: Fix apiurl

[Hellkaros]

Closes #6673

Checklist:

• Updated extVersionCode value in build.gradle for individual extensions
• Updated overrideVersionCode or baseVersionCode as needed for all multisrc extensions
• Referenced all related issues in the PR body (e.g. "Closes #xyz")
• Added the isNsfw = true flag in build.gradle when appropriate
• Have not changed source names
• Have explicitly kept the id if a source's name or language were changed
• Have tested the modifications by compiling and running the extension through Android Studio
• Have removed web_hi_res_512.png when adding a new extension

[euxande]

Eu sou novo com essa coisa de programação. Onde eu coloco esses códigos pra poder executar o slimeread?

[choppeh]

@MrRobotCoder I had to make changes in the same place in SlimeRead to include another source. 😔🙏 PR: #6780

[Hellkaros]

No problem @choppeh your change to the apiurl is great... I'll close this PR since yours is more complete and automatically retrieves the URL within the script. Can you just push another commit to the build.gradle changing the overrideVersionCode from 15 to 16?

Since I think choppeh's solution is better implemented, I'm closing this PR.