Support for linkifying headlines

[therealpxc]

Go-org already supports setting link anchors if a headline's CUSTOM_ID property, if set. This is great. 😁

However, one thing it doesn't do that I miss from Hugo's Goldmark exporter is make it so it's easy to grab a headline's anchor link while looking at the headline, without going back to a table of contents or something like that. (For Markdown, Hugo will put little links next to each headline that show up when you hover.)

Org mode itself supports a very similar feature in its HTML exporter, whereby the headline itself is made into a link on the page, which points to its own anchor. This is controlled in Emacs by the org-html-self-link-headlines variable.

It would be great if go-org supported an equivalent option!