Fixed the header bug and added abstract example

• \usepackage[T1]{fontenc} was causing math rendering bug because it should only be used with PDFtex engine. Let pandoc handle this.
• Added an example of including the abstract to academic-static example

Fixed the classoption typos

Had classoption: ["onepage", "openany"] instead of classoption: ["oneside", "open=any"] for scrbook in the titlepages article.qmd example files.
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