Documentation to-dos

[st--]

• page-flip behaviour (see Annotations do not behave well across page flips #12)
• clarify direction of the annotation arrows for when you want to change the styling (see Option \tikzset{annotate equations/arrow/.style={->}} does not work #19)
• add mention that one should always finish with % after the \annotate(two) command to avoid inadvertent spacing issues (see The annotate command adds a line after the equation if used outside the equation #24)