v0.1.8

• Add new conversions for:
  • ??citation??
  • ^superscript^
  • ~subscript~
  • {panel}...{panel}
• Add space before and after user mention (@username) if it adjacent to a text
• Allow punctuation marks come after the user mention (@username) without a space
• Add a line break before and after a table if only it adjacent to a text