Make conceal case sensitive

vim/after/syntax/markdown.vim

@@ -4,13 +4,13 @@
 
 " Custom conceal
 let dtd_ignore_case=0
-syntax match todoCheckbox "\[\ \]" conceal cchar=☐
-syntax match todoCheckbox "\[X\]" conceal cchar=☒
-syntax match todoCheckbox "\[x\]" conceal cchar=☑
+syntax match todoCheckbox /\[\ \]/ conceal cchar=☐
+syntax match todoCheckbox /\C\[X\]/ conceal cchar=☒
+syntax match todoCheckbox /\C\[x\]/ conceal cchar=☑
 
-syntax match todoCheckbox "- \[\ \]" conceal cchar=☐
-syntax match todoCheckbox "- \[X\]" conceal cchar=☒
-syntax match todoCheckbox "- \[x\]" conceal cchar=☑
+syntax match todoCheckbox /[*-] \[\ \]/ conceal cchar=☐
+syntax match todoCheckbox /\C[*-] \[X\]/ conceal cchar=☒
+syntax match todoCheckbox /\C[*-] \[x\]/ conceal cchar=☑
 
 hi def link todoCheckbox Todo