WeebCentral: Exclude special characters

[dngonz]

Closes #7157

There are special characters that when searching gives an error or return empty results

Tested with:

• Don't Blush, Sekime-san!
• Golden Time (Umechazuke)
• #Killstagram
• ID:INVADED #BRAKE BROKEN

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

[Hellkaros]

I think the best approach wouldn't be to exclude special characters, especially because if you search the site for just '!', manga titles will show up. The extension doesn't need an update since the path used to develop the search was based on 'advanced search.' However, on the site, if you go to 'advanced search' and search for 'Don't Blush, Sekime-san!', there won't be any results. In this case, it would be a matter of modifying the searchMangaRequest method to perform the search using 'Quick search' instead of 'advanced search.'