fix(tutor): set a value for ":syntax iskeyword" (#27833)

Problem: "NOTE"s, inline Vim script code, and links ending in digits may not be
highlighted correctly within the :Tutor.

Solution: set an explicit value for ":syntax iskeyword" that includes digits. Do
it after ":syntax include"s, so the included syntax/sh.vim doesn't mess with the
value.

Increase screen test width so all text within the conclusion section is visible.

Co-authored-by: Sean Dewar <6256228+seandewar@users.noreply.github.com>

runtime/syntax/tutor.vim

@@ -8,6 +8,8 @@ syn include @TUTORSHELL syntax/sh.vim
 unlet b:current_syntax
 syn include @VIMNORMAL syntax/vimnormal.vim
 
+syn iskeyword @,-,_,48-57
+
 syn match tutorLink /\[.\{-}\](.\{-})/ contains=tutorInlineNormal
 syn match tutorLinkBands /\[\|\]\|(\|)/ contained containedin=tutorLink,tutorLinkAnchor conceal
 syn match tutorLinkAnchor /(.\{-})/ contained containedin=tutorLink conceal