Everywhere: Add sv suffix to strings relying on StringView(char const*)

Each of these strings would previously rely on StringView's char const*
constructor overload, which would call __builtin_strlen on the string.
Since we now have operator ""sv, we can replace these with much simpler
versions. This opens the door to being able to remove
StringView(char const*).

No functional changes.

Userland/Libraries/LibMarkdown/ContainerBlock.cpp

@@ -125,7 +125,7 @@ OwnPtr<ContainerBlock> ContainerBlock::parse(LineIterator& lines)
         }
 
         if (!paragraph_text.is_empty())
-            paragraph_text.append("\n");
+            paragraph_text.append('\n');
         paragraph_text.append(*lines++);
     }