Add possibility to display line numbers in Markdown files

[kevung]

• Gitea version (or commit ref):
  1.11.4 built with GNU Make 4.1, go1.13.9 : bindata, sqlite, sqlite_unlock_notify
• Git version:
• Operating system: Linux 5.6.7-arch1-1
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
  • Not relevant
• Log gist:

Description

The line numbers are displayed for text files, but since Markdown is processed on the web interface, line numbers are not displayed.

Is it possible to display line numbers in Markdown files from the web interface?
In my case, I write project documentation in Markdown and I would like to be able to refer/quote some Markdown content with the line numbers inside issues.

Thanks :)

[kevung]

This feature has also been asked on Github:

• View raw non-rendered markdown source with line numbers on file blob show view isaacs/github#297

• Linking to lines within a Markdown text file? holman/ama#305