Lektor-tags

Bugs Fixed

- Convert module to package, enabling us to ship the default template
as package data. ([26][])

[26]: https://github.com/lektor/lektor-tags/pull/26

Bugs Fixed

- Ignore duplicate tags (on a single page) when counting. ([25][])
- When applicable, limit tags to those specified in the
[`tags`][config-tags] config setting ([25][])

[25]: https://github.com/lektor/lektor-tags/pull/25
[config-tags]: https://github.com/lektor/lektor-tags#tags

Added a `tagweights` jinja global that provides reference counts of
tags and other bits useful for constructing tag clouds or similar types
of tag lists. ([19][] — Thank you Louis Paternault!)

[19]: https://github.com/lektor/lektor-tags/pull/19

Switch to setup.cfg and a PEP517-build.

Update to the README as well as test, pre-commit and CI configuration.

Fixes 2, persisting self.pad. Version bump.