Add icons customizability for modularity

[onweru]

Split the icons template into self-contained blocks

Pull Request type

Please check the type of change your PR introduces:

• Bug-fix
• Feature (functionality, design, translations, etc.)
• Documentation change
• Project management (tests, CI, GitHub configuration, etc.)
• Other (please describe):

Current state

Currently, all clarity users are forced to load ~ dozen social icons which they very well may not need on their websites. This situation makes the html size of their pages unnecessarily bloated.

I have been reluctant merging PRs for icons. However, after merging #404, I realized that we could actually modularize things so that users can add icons freely while avoiding the aforementioned problem.

This represents a breaking change for existing theme users. To update, they will need add to config/_default/params.toml a generic list icons.

Issue Number(s):

Proposed changes

Screenshots, if applicable

Checklist

• Bug-fixes and new features: I have tested locally with the latest release of Hugo extended. This requirement is a standard.
• Bug-fixes, new features, and doc changes: I have updated the relevant documentation as part of this PR.
• All PRs: I have signed off (using git commit -s ...), or if not possible due to developer environment constraints, will comment below confirming that I am adhering to the Developer Certificate of Origin.

[chipzoller]

What should we do with this, @onweru?