feat: display accurate copyright years on pages

[jamesericdavidson]

tl;dr Implementation for #222.

• Pages which are not of kind page continue to use now.Year
• Pages which do not declare .Date also use now.Year
• Pages which declare .Date use it instead of now.Year
• Pages which declare .Lastmod and .Date use both dates in a range, instead of now.Year

A long copyright string will overflow the .footer container, ergo some assistance on the CSS side would be greatly appreciated. :smiley:

N.B. Copyright is described by Hugo here: https://gohugo.io/methods/site/copyright/

• ~css fixes~ See #234
• [x] docs (advanced)
• [x] screenshots
• config opt-in ? copyright is only displayed if it exists in config.toml; I'd argue this isn't necessary
• add dateFormat to config.toml ?
  • add Lastmod to any relevant exampleSite pages for illustration ?

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[jamesericdavidson]

Screenshots

Non-page kinds:

Page without .Date or .Lastmod:

Pages with .Date but not .Lastmod:

Pages with .Date and .Lastmod:

Sites with copyright:

[jamesericdavidson]

@yashmehrotra @526avijitgupta I hope this suits. Look forward to your review :+1:

[jamesericdavidson]

See #234

[yashmehrotra]

@jamesericdavidson I think we can leave the CSS problem for now since it only happens with very large texts which is not the usual case. Can you create a separate issue for this ?

I'll merge this for now, thanks for your contribution

[jamesericdavidson]

@yashmehrotra Brilliant, thanks Yash. Will do :+1: