document linkifyHeaderStyle in default.js

Signed-off-by: hoijui <hoijui.quaero@gmail.com>

Author: hoijui

lib/config/default.js

@@ -163,5 +163,18 @@ module.exports = {
   allowGravatar: true,
   allowPDFExport: true,
   openID: false,
+  // linkifyHeaderStyle - How is a header text converted into a link id.
+  // Header Example: "3.1. Good Morning my Friend! - Do you have 5$?"
+  // * 'keep-case' is the legacy CodiMD value.
+  //    Generated id: "31-Good-Morning-my-Friend---Do-you-have-5"
+  // * 'lower-case' is the same like legacy (see above), but converted to lower-case.
+  //    Generated id: "#31-good-morning-my-friend---do-you-have-5"
+  // * 'gfm' _GitHub-Flavored Markdown_ style as described here:
+  //    https://gist.github.com/asabaylus/3071099#gistcomment-1593627
+  //    It works like 'lower-case', but making sure the ID is unique.
+  //    This is What GitHub, GitLab and (hopefully) most other tools use.
+  //    Generated id:   "31-good-morning-my-friend---do-you-have-5"
+  //    2nd appearance: "31-good-morning-my-friend---do-you-have-5-1"
+  //    3rd appearance: "31-good-morning-my-friend---do-you-have-5-2"
   linkifyHeaderStyle: 'keep-case'
 }