Format `{\it foo}` to `\textit{foo}`

[tdegeus]

{em ...} -> \emph{...} {it ...} -> \textit{...}

[tdegeus]

The best is to allow regex input for texclean.

[tdegeus]

This could also allow, for example, to add a newline after sections:

\paragraph{...}
My text

would become

\paragraph{...}

My text

The problem is however that regex does not support matching brackets

[tdegeus]

See https://github.com/tdegeus/texplain/issues/112 for regex finding matching brackets