preamble.tex

\usepackage{booktabs}
\usepackage{amsthm}
\usepackage[many]{tcolorbox}
\usepackage{graphicx}
\usetikzlibrary{calc}

\makeatletter
\def\thm@space@setup{%
  \thm@preskip=8pt plus 2pt minus 4pt
  \thm@postskip=\thm@preskip
}
\makeatother

% Create our general design
\newtcolorbox{customBlockImage}[2][]{
  enhanced,
  top=10pt,
  bottom=10pt,
  colframe = white,
  width=\textwidth,
  boxsep=5pt,
  arc=1pt,
  outer arc=1pt,
  leftupper=1.5cm,
overlay={
    \node[anchor=west]
      at ([xshift=10pt] $ (interior.north west)!0.5!(interior.south west) $ )
       {{\setkeys{Gin}{width=3em,keepaspectratio}\includegraphics{#2}}};},
#1}

% Define the colours to match the CSS
\definecolor{cexercise}{HTML}{A1BE95}
\definecolor{cnote}{HTML}{92AAC7}
\definecolor{cwarning}{HTML}{ED5752}

 % Create the new environments for R Markdown
\newenvironment{rmdexercise}
  {\begin{customBlockImage}[colback=cexercise]{images/exercise}}
  {\end{customBlockImage}}

\newenvironment{rmdnote}
  {\begin{customBlockImage}[colback=cnote]{images/note}}
  {\end{customBlockImage}}

\newenvironment{rmdwarning}
  {\begin{customBlockImage}[colback=cwarning]{images/warning}}
  {\end{customBlockImage}}

\urlstyle{tt}