chore: Added support for lhs compile with vimtex

.latexmkrc

@@ -0,0 +1,14 @@
+# Use subroutine to do preprocessing and running pdflatex
+$pdflatex = 'internal mylatex %B %O';
+sub mylatex {
+  my $base = shift @_;
+  my $tex = "$base.tex";
+
+  # Run the preprocessor
+  system('lhs2TeX', '--poly', '-o', $tex, "$base.lhs") == 0 or return $?;
+  # Run pdflatex
+  my $return = system('pdflatex', @_, $tex);
+  system "echo INPUT $base.lhs >> $aux_dir1$base.fls";
+  return $return;
+}
+