Add rss icon next to social accounts

Update rss link included in header

Rss link generation in hugo documentation is wrong according to this
issue. Replace it with the correct links.

Issue: gohugoio/hugoDocs#369

Turn off word wrapping for code

Add additional supported social media links

Description:
I've updated it to read `devto` (which is the proper reference).

Note: Documentation update

Description:
The social.md file lists several other options for social media that
were not included in the official documentation. I have added them
here for completeness (alternatively, a note could just be made in
the README which points to said file to see the most up-to-date list
of supported accounts).

Note: Documentation update

fix(layout): Fixed RSS link generation

List to descend in publish date

This was the old behaviour, but seems to have changed.

Using Highlight.js, when I use fenced code blocks, the text wraps which doesn't look very nice.

This is a bit of a brute force fix for the issue. There might be a better way of doing it, but this
works for me for now.

fix(layout): Make author image url honor baseURL

Don't show "PUBLISHED ON" for content without dates

Otherwise posts without a `date` attribute in their front matter will
use a zero `time.Time`.
This results in the post showing `PUBLISHED ON JAN 1, 0001`

Adding xing as social link

Hugo v0.20.2, fixed 'error calling len: len of untyped nil' related w…

Fix untyped nil error

Add support for custom Highlightjs themes and optional languages

Fix small typo in example site config

Social icons for medium, dev.to() and angellist