Mangadex markdown cleanup removes --- only with newline

[spicemace]

Tables are affected if any --- is removed.
Tables need other handling too in another change.
Fixes #872

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

[AwkwardPeak7]

please test your changes

[spicemace]

Tested with entry that has both :--- and \n--- in description, removes everything after latter, no longer removes everything after former. Table contents display in full, but following section is correctly removed.

[AwkwardPeak7]

please give example manga where this behavior can be seen

[spicemace]

please give example manga where this behavior can be seen

NSFW/R18

https://mangadex.org/title/c18875a8-859d-44e5-ac64-aad167862363

Before change, table cuts off after Namespace Tags row. After change, table is displayed fully, and description ends at line before Additional Links.

[AwkwardPeak7]

please bump version again