feat: add last modified date to post meta

[margau]

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

This PR adds the "last modified" date to the post meta section in case a last modified is present and is not equal to the original post date.

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

Closes #1037

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.
• 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

[danielpetre]

Very useful commit, thanks OP !

[Chow-Ray]

Very useful commit too, thanks OP !

[j0hax]

I'm also very interested in seeing this merged!

[xuhdev]

Are we still interested in this change?

[danielpetre]

i am !

[woadey]

This is great