fix: fix safari 14 throw Invalid regular expression error

lib/converters.js

@@ -177,7 +177,7 @@ converters.table = (input, json2md) => {
         (Array.isArray(row) ? row : input.headers.map(col_id => row[col_id]))
             .map(cell => json2md(cell))
             .map(cell => parseTextFormat(cell))
-            .map(cell => cell.replace(/(?<!(\\))\|/, "\\|"))
+            .map(cell => cell.replace(/([^\\])\|/, "$1\\|"))
             .join(" | ")
     ).join("\n") + " |";