feat(b-drodpown-item-button, b-drodpown-item-button): add button-class and link-class prop

[pburdette]

Describe the PR

Reason for this PR: It would be nice to use utility classes on this button without having to introduce new CSS into a codebase.

• Adds the button-class prop to the b-dropdown-item-button component.
• Adds the link-class prop to the b-dropdown-item component.
• Updates dropdown-item-button.spec.js with a new test
• Updates dropdown-item.spec.js with a new test

PR checklist

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

• Bugfix
• Feature
• Enhancement
• ARIA accessibility
• Documentation update
• Other (please describe)

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

• No
• Yes (please describe)

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.

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

• Includes documentation updates (including updating the component's package.json for slot and event changes)
• Includes any needed TypeScript declaration file updates
• New/updated tests are included and passing (if required)
• Existing test suites are passing
• CodeCov for patch has met target
• 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)

[codecov]

Codecov Report

Merging #5014 into dev will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev    #5014   +/-   ##
=======================================
  Coverage   99.93%   99.93%           
=======================================
  Files         275      275           
  Lines        6423     6423           
  Branches     1620     1620           
=======================================
  Hits         6419     6419           
  Misses          3        3           
  Partials        1        1           

Impacted Files	Coverage Δ
src/components/dropdown/dropdown-item-button.js	100.00% <ø> (ø)
src/components/dropdown/dropdown-item.js	100.00% <ø> (ø)

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[pburdette]

@tmorehouse does this seem like a prop that would be okay to add? Wanted to get your opinion before I move onto finishing the rest of the checklist. 🙇

[tmorehouse]

@beardedpayton just made a few tweaks, and updated the package.json component meta data to indicate the version the prop was added, as well as description for it. And added a similar prop for <b-dropdown-item>

[pburdette]

@tmorehouse thanks! I just added a test for the linkClass prop as well 👍

Does this PR need anymore attention?

[tmorehouse]

I think it is good as is now 👍

[jacobmllr95]

Thanks @pburdette!

[pburdette]

Thanks @jackmu95 and @tmorehouse 🎉

[tmorehouse]

@pburdette BootstrapVue v2.9.0 has been released.