fix: Support \S and \P in math mode (#2977)

Co-authored-by: Erik Demaine <edemaine@mit.edu>

docs/supported.md

@@ -662,8 +662,8 @@ In cases where KaTeX fonts do not have a bold glyph, `\pmb` can simulate one. Fo
 |$\text{\textbraceleft}$ `\text{\textbraceleft}`|$\Diamond$ `\Diamond`|$\text{\textdegree}$ `\text{\textdegree}`
 |$\text{\textbraceright}$ `\text{\textbraceright}`|$\lozenge$ `\lozenge`|$\mho$ `\mho`
 |$\text{\textbackslash}$ `\text{\textbackslash}`|$\blacklozenge$ `\blacklozenge`|$\diagdown$ `\diagdown`
-|$\text{\P}$ `\text{\P}`|$\star$ `\star`|$\diagup$ `\diagup`
-|$\text{\S}$ `\text{\S}`|$\bigstar$ `\bigstar`|$\flat$ `\flat`
+|$\text{\P}$ `\text{\P}` or `\P`|$\star$ `\star`|$\diagup$ `\diagup`
+|$\text{\S}$ `\text{\S}` or `\S`|$\bigstar$ `\bigstar`|$\flat$ `\flat`
 |$\text{\sect}$ `\text{\sect}`|$\clubsuit$ `\clubsuit`|$\natural$ `\natural`
 |$\copyright$ `\copyright`|$\clubs$ `\clubs`|$\sharp$ `\sharp`
 |$\circledR$ `\circledR`|$\diamondsuit$ `\diamondsuit`|$\heartsuit$ `\heartsuit`
@@ -671,7 +671,7 @@ In cases where KaTeX fonts do not have a bold glyph, `\pmb` can simulate one. Fo
 |$\circledS$ `\circledS`|$\spadesuit$ `\spadesuit`|$\spades$ `\spades`
 |$\text{\textcircled a}$ `\text{\textcircled a}`|$\maltese$ `\maltese`|$\minuso$ `\minuso`|
 
-Direct Input: $£ ¥ ∇ ∞ · ∠ ∡ ∢ ♠ ♡ ♢ ♣ ♭ ♮ ♯ ✓ …  ⋮  ⋯  ⋱  !$ ‼ ⦵
+Direct Input: § ¶ $ £ ¥ ∇ ∞ · ∠ ∡ ∢ ♠ ♡ ♢ ♣ ♭ ♮ ♯ ✓ …  ⋮  ⋯  ⋱  !$ ‼ ⦵
 
 ## Units