feat(b-pagination, b-pagination-nav): add page button class props and option to show first/last page numbers (closes #4597, #4533)

[jacobmllr95]

Describe the PR

This PR add adds following new props to the <b-pagination> and <b-pagination-nav> components:

• first-class - Adds a custom class to the first page button.
• prev-class - Adds a custom class to the previous page button.
• next-class - Adds a custom class to the next page button.
• last-class - Adds a custom class to the last page button.
• page-class - Adds a custom class to the page buttons.
• ellipsis-class - Adds a custom class to the ellipsis elements.
• first-number - Show the first page number in favor of the first-text. Will move the first page button after the previous page button.
• last-number - Show the last page number in favor of the last-text. Will move the last page button before the next page button.

Closes #4597, Closes #4533.

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 #4622 into dev will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              dev    #4622      +/-   ##
==========================================
+ Coverage   99.92%   99.92%   +<.01%     
==========================================
  Files         253      253              
  Lines        5230     5259      +29     
  Branches     1388     1399      +11     
==========================================
+ Hits         5226     5255      +29     
  Misses          3        3              
  Partials        1        1

Impacted Files	Coverage Δ
src/mixins/pagination.js	100% <100%> (ø)	⬆️

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[tmorehouse]

I think we might need a bit more conditional code in the render function, as the 1 button flips between being a bookend button and a regular page number button. (similar for the last page button). i.e. the hidden aria label switches from "go to first page" to "goto page 1", depending on how it is rendered (i.e. what the current page number is).

Otherwise, good first stab at this.

Perhaps, do not render the "go to first page" button at all, and only render the extra page 1 button if the first ellipsis is showing (although we should not allow hiding ellipsis in this mode)

Or, we filter out the regular page 1 button from the page array, and always show the first page bookend button?

[tmorehouse]

I definitely like the visual rendering look of it.

[tmorehouse]

We'll also need to add an example (or at least some verbiage) in both pagination and pagination-nav docs