Add option to add word count to metadata. Closes #735

[thiagowfx]

Reading time is subjective and relative. Word count is absolute and a
more reliable and traditional proxy to estimate how long a post is. It's
not perfect, and there are variations across languages, hence an option
would leave it to users to decide whether it's relevant to their use
cases.

Introduce a ShowWordCount option and use it in post_meta.html.

Hugo supports word counts natively, c.f.
https://gohugo.io/variables/page/#page-variables

What does this PR change? What problem does it solve?

c.f. commit description above

Was the change discussed in an issue or in the Discussions before?

See #735

PR Checklist

• This change adds/updates translations and I have used the template present here.
• I have enabled maintainer edits for this PR.
• I have verified that the code works as described/as intended. --> tested on my blog with 'en' and 'pt', verified it works as expected
• [N/A] This change adds a Social Icon which has a permissive license to use it.
• This change does not include any CDN resources/links.
• This change does not include any unrelated scripts such as bash and python scripts.
• This change updates the overridden internal templates from HUGO's repository.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[thiagowfx]

Notes:

• I only added translations that I am confident to be correct. If you'd like I could add them all with google translate but I wouldn't be sure whether they are accurate.
• I couldn't find anywhere to document this option in. If there's a suitable to do so let me know, happy to send docs alongside this PR.

[adityatelange]

Thanks @thiagowfx!