Avoid looping multiple times across entries

Bumps [github.com/prometheus/client_golang](https://github.com/prometheus/client_golang) from 1.7.1 to 1.8.0.
- [Release notes](https://github.com/prometheus/client_golang/releases)
- [Changelog](https://github.com/prometheus/client_golang/blob/master/CHANGELOG.md)
- [Commits](https://github.com/prometheus/client_golang/compare/v1.7.1...v1.8.0

)

Signed-off-by: dependabot[bot] <support@github.com>

Bumps [github.com/PuerkitoBio/goquery](https://github.com/PuerkitoBio/goquery) from 1.5.1 to 1.6.0.
- [Release notes](https://github.com/PuerkitoBio/goquery/releases)
- [Commits](https://github.com/PuerkitoBio/goquery/compare/v1.5.1...v1.6.0

)

Signed-off-by: dependabot[bot] <support@github.com>

- Add support for picture HTML tag
- Add support for srcset, media, and sizes attributes to img and source tags

Reducing these values avoid going over the max number of file descriptors when refreshing lot of feeds

Prevent sub and sup from affecting line-height.

Set touch-action on .items to prevent browser navigation.

Move font-family specific CSS to the appropriate file.

Update primary font-family for UI to be even more
compatible with various operating systems.

Make .entry-content font-weight variable depending
on font-family used.

Also includes few database improvements:

- Speed up entries clean up with an index and a goroutine
- Avoid the accumulation of enclosures for some feeds