Generate canonicals inline

[budnix]

Context

The PR modifies the Docs generator in a way that generates the canonical URLs inline in HTML. The canonical URLs are generated from the manually added canonicalUrl property of the frontmatter object and are not generated automatically as before the changes.

The fix should be applied to all VuePress-based Docs versions.

[skip changelog]

How has this been tested?

I tested the changes on staging env.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)

Related issue(s):

1. solves the canonical part of the https://github.com/handsontable/dev-handsontable/issues/1815

Checklist:

• [x] I have reviewed the guidelines about Contributing to Handsontable and I confirm that my code follows the code style of this project.
• [x] I have signed the Contributor License Agreement
• [x] My change requires a change to the documentation.

[github-actions[bot]]

Launch the local version of documentation by running:

npm run docs:review 7a0b0171e3e5d867f60234e5d52019be9f404127