This commmit prepares for the addition of Goldmark as the new Markdown renderer in Hugo.
This introduces a new `markup` package with some common interfaces and each implementation in its own package.
See #5963
Changes fall into one of the following:
- gofmt -s
- receiver name is inconsistent
- omit unused 2nd value from range
- godoc comment formed incorrectly
- err assigned and not used
- if block ends with a return statement followed by else
All config variables starts with low-case and uses camelCase.
If there is abbreviation at the beginning of the name, the whole
abbreviation will be written in low-case.
If there is abbreviation at the end of the name, the
whole abbreviation will be written in upper-case.
For example, rssURI.
