chore(docs): improve icons page

[jacobmllr95]

Describe the PR

This PR makes some styling tweaks to the icons page to bring it more in line with the Bootstrap counterpart.

Missed documentation updates after the Bootstrap Icons v1.0.0-alpha5 update are also included.

PR checklist

What kind of change does this PR introduce? (check at least one)

• Bugfix (fixes a boo-boo in the code) - fix(...), requires a patch version update
• Feature (adds a new feature to BootstrapVue) - feat(...), requires a minor version update
• Enhancement (augments an existing feature) - feat(...), requires a minor version update
• ARIA accessibility (fixes or improves ARIA accessibility) - fix(...), requires a patch or minor version update
• Documentation update (improves documentation or typo fixes) - chore(docs), requires a patch version update
• Other (please describe)

Does this PR introduce a breaking change? (check one)

• No
• Yes (please describe since breaking changes require a minor version update)

The PR fulfills these requirements:

• It's submitted to the dev branch, not the master branch
• When resolving a specific issue, it's referenced in the PR's title (i.e. [...] (fixes #xxx[,#xxx]), where "xxx" is the issue number)
• It should address only one issue or feature. If adding multiple features or fixing a bug and adding a new feature, break them into separate PRs if at all possible.
• The title should follow the Conventional Commits naming convention (i.e. fix(alert): not alerting during SSR render, docs(badge): update pill examples, chore(docs): fix typo in README, etc). This is very important, as the CHANGELOG is generated from these messages, and determines the next version type (patch or minor).

If new features/enhancement/fixes are added or changed:

• Includes documentation updates
• Includes component package.json meta section updates (prop, slot and event changes/updates)
• Includes any needed TypeScript declaration file updates
• New/updated tests are included and passing (required for new features and enhancements)
• Existing test suites are passing
• CodeCov for patch has met target (all changes/updates have been tested)
• The changes have not impacted the functionality of other components or directives
• ARIA Accessibility has been taken into consideration (Does it affect screen reader users or keyboard only users? Clickable items should be in the tab index, etc.)

If adding a new feature, or changing the functionality of an existing feature, the PR's
description above includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

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[codecov]

Codecov Report

Merging #5579 into dev will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##               dev     #5579    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files          277       277            
  Lines         9014      9379   +365     
  Branches      2494      2497     +3     
==========================================
+ Hits          9014      9379   +365     

Flag	Coverage Δ
#unittests	100.00% <100.00%> (ø)

Impacted Files	Coverage Δ
src/icons/icons.js	100.00% <ø> (ø)
src/icons/plugin.js	100.00% <ø> (ø)
src/components/form-tags/form-tags.js	100.00% <100.00%> (ø)

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