Extending a John Kormylo Answer for Color Shading a Portion of a Paragraph to Produce Bold Text as Well

Question

This post is an extension of the question posed in How to Contiguously Shade a Portion of a Paragraph with Color

Consider the code

\documentclass{book}
\usepackage{xcolor}
\colorlet{soulred}{red!25}
\usepackage{tikzpagenodes}
\usetikzlibrary{tikzmark,calc}

\newlength{\markheight}

\begin{document}
\thispagestyle{empty}
\large

\begin{tikzpicture}[overlay, remember picture]
\coordinate (A) at (pic cs:start);
\coordinate (B) at (pic cs:end);
\pgfextracty{\markheight}{\pgfpointdiff{\pgfpointanchor{B}{center}}{\pgfpointanchor{A}{center}}}% difference in baselines
\ifdim\markheight<\baselineskip% same line
  \fill[color=soulred] ($(A)+(-2pt,\ht\strutbox)$) rectangle ($(B)+(2pt,-\dp\strutbox)$);
\else
  \ifdim\markheight<3\baselineskip
    \fill[color=soulred] ($(A)+(-2pt,\ht\strutbox)$) rectangle ($(A -| current page text area.east)+(2pt,-\dp\strutbox)$);
    \fill[color=soulred] ($(B -| current page text area.west)+(-2pt,\ht\strutbox)$) rectangle ($(B)+(2pt,-\dp\strutbox)$);
  \else
    \fill[color=soulred] ($(A)+(-2pt,\ht\strutbox)$) rectangle ($(A -| current page text area.east)+(2pt,-\dp\strutbox)$);
    \fill[color=soulred] ($(A -| current page text area.west)+(-2pt,-\dp\strutbox)$) rectangle ($(B -| current page text area.east)+(2pt,\ht\strutbox)$);
    \fill[color=soulred] ($(B -| current page text area.west)+(-2pt,\ht\strutbox)$) rectangle ($(B)+(2pt,-\dp\strutbox)$);
  \fi
\fi
\end{tikzpicture}

Here is some text. \tikzmark{start}Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text.  Here is some text. Here is some text. Here is some text.\tikzmark{end}

\vspace*{10pt}

Here is some text. \tikzmark{start}\textbf{Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text. Here is some text.  Here is some text. Here is some text. Here is some text.}\tikzmark{end}
\end{document} 

which produces

I have made bold the color shaded text in a usual way---by using \textbf applied to a specific portion of the text---though it seems to neutralize the use of the \tikzmark command in the first paragraph. (Not sure why.)

I have a document consisting of a few hundred pages which I would, in addition to color shading some of the text, I would like to make such text bold as well. And I would like to avoid, if possible, using \textbf throughout the document many times.

I would like to be able to have another command (an alternative to \tikzmark, say, something like \tikzmarkbold) which does the shading of \tikzmark, but also makes the shaded text bold, automatically.

I would like to have the choice to use either of the two commands in the document.

QUESTION: Is it possible to modify the above code to accomplish this; and if so, how?

Thank you.