add i18n translation support

[jan-xyz]

With this Draft PR I want to get early feedback on my approach for tackling #108 and I would really appreciate some feedback from @budparr, @regisphilibert and anyone else involved.

I implemented a few strings that are easily visible but that should also include most of the strings. This theme is actually quiet and there isn't much text to translate in the first place I think.

I switched to this branch for my own blog and you can see the changes live at: https://blog.jan-steinke.de

So far I only have the translations for "de"(German) and "en"(English). The multi language support build into Hugo should default to "en" if I can trust the documentation, I haven't actually checked if this is true but it should make sure that anyone using this theme with single language should be fine as well.

defaultContentLanguage sets the project’s default language. If not set, the default language will be en.

One thing I consciously removed is the support for recent_copy and read_more_copy as I understood that these are for multi language support and should be unnecessary if we build into i18n support.

Things need clarification before WIP is done:

• removal of ..._copy parameters
• keep it for backwards compatibility (add i18n translation support #156 (comment))
• which languages should be supported with the first implementation
• anything else?

[echarp]

This looks awesome! 👍

You don't like using "T" instead of the longer "i18n" command? Shorter but not as clear?

I'll help with french if possible.

[jan-xyz]

Thanks, any support is appreciated! If you want make a PR to my branch with French translations. I can also see if I can give you Push rights on my branch directly, if you want.

I saw the T option but don't really have a strong opinion on it, whatever works best for the project. Maybe something else to decide on now?

[budparr]

Thanks, @jan-xyz! @regisphilibert has suggested we use this construction for the strings:

{{$.Param "read_more_copy" | default (i18n "readMore") }}

otherwise, this could be a breaking change for many.

[jan-xyz]

Sounds good to me and I fixed it with your suggestion. Is there anything else that you would like to see with this?

[budparr]

Looks good to me. I'm going to run it locally before merging, but will try to get to that tonight. Thanks @jan-xyz!

[jan-xyz]

No need to thank me :) I'm benefiting as well from this project.