markdown: replace icons for headings

lua/crentist/lazy/markdown.lua

@@ -6,6 +6,9 @@ return {
     opts = {
        completions = {
            blink = { enabled = true }
+       },
+       heading = {
+           icons = { '󰬺 ', '󰬻 ', '󰬼 ', '󰬽 ', '󰬾 ', '󰬿 ' },
        }
     },
 }