Switch to goldmark

[parsiya]

Hugo v0.60 and up uses goldmark, we can switch to it and see how it holds up.

Note: remember to modify the readme and the sample config. Mention the goldmark switch.

Goldmark does not have a setting to open links in a new tab unlike Blackfriday. We can use render hooks, but the render-link from the Hugo docs website does not work on linkify links. E.g., if I have [example.net](https://example.net) in my page, it will open it in a new tab but just https://example.net (which is turned into a link by Goldmark's linkify extension) does not open in a new tab. Need to figure out a way to fix it. Maybe, as on Hugo forums?

I gave up and said we can use Blackfriday if we want that functionality in the readme.

[parsiya]

Also need to bump the min version to 0.63 (and change the version in parsiya.net, too).

[parsiya]

Also need to change the highlight settings at https://gohugo.io/getting-started/configuration-markup#highlight.

Need to change the readme and the sample config and the example site config.

[parsiya]

Tracked in the markup branch https://github.com/parsiya/Hugo-Octopress/tree/markup

[parsiya]

Fixed in e1b3a5ca4e373bc1d9819a9cfe0d4d56468c3875