✨ feat(footer): add configurable copyright notice

[welpo]

TL;DR

Add a dynamic and translatable copyright notice for the footer.

Description

This PR adds a feature that allows users to add a custom copyright notice in the footer of their site.

Key features:

1. Dynamic year insertion:

   • Users can use the $CURRENT_YEAR placeholder to automatically have the current year inserted into the copyright notice, eliminating the need to manually update it each year.

2. Markdown support:

   • Enhanced the notice with Markdown support, letting users easily add links, emphasize text, or make other necessary formatting changes.

3. Multi-language support:

   • For sites in multiple languages, there's an option to set a translated version of the copyright.

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Changes

1. TOML configuration:

   • Added copyright and translate_copyright options.
   • Provided comments explaining the purpose and usage of each option.

2. Tera template:

   • Updated the footer template to include the new copyright feature.
   • Ensured that the translated version is used based on site's language configuration and user preference.

3. Footer CSS:

   • Centered the footer text and removed the margin between paragraphs.

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Screenshots:

• A simple notice:

  [extra]
  copyright = "© $CURRENT_YEAR welpo

  

• A more complex notice, with Markdown:

  [extra]
  copyright = "© $CURRENT_YEAR Your Name • Unless otherwise noted, the content in this website is available under the [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/) license."

  

[Jieiku]

Such a clean implementation! You may have noticed I was dancing around the Year in abridge. This is a much better solution! Thank You!

[welpo]

Hehe thanks I looked at Abridge and saw so many config variables… Decided to keep it as simple as possible! (If only I could also auto-detect the translated copyright without an extra variable…)

[welpo]

Just added the option to also replace $SEPARATOR to the config.extra.separator variable on f1edbba.

So this Copyright notice:

Can now be set with:

[extra]
copyright = "© $CURRENT_YEAR Your Name $SEPARATOR Unless otherwise noted, the content in this website is available under the [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/) license."