feat(number-field): add missing `--mod-*` tokens

Description

Adds two more --mod-* tokens as per https://github.com/adobe/spectrum-web-components/issues/4527 --mod-textfield-border-width and --mod-textfield-border-color.

I did not add a mod token for --spectrum-textfield-corner-radius because the focus outline would look weird if you modify this CSS property.

Related issue(s)

https://github.com/adobe/spectrum-web-components/issues/4527

Motivation and context

Consumers are able to override border's width and color when hide-stepper is true.

How has this been tested?

[ ] Test case 1
1. Go here
2. Open the developer console and define --mod-textfield-border-width and --mod-textfield-border-color on the sp-number-field component
3. The changes should be visible on the component.

Screenshots (if appropriate)

Types of changes

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)
[ ] Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)

Checklist

[x] I have signed the Adobe Open Source CLA.
[x] My code follows the code style of this project.
[x] If my change required a change to the documentation, I have updated the documentation in this pull request.
[x] I have read the CONTRIBUTING document.
[ ] I have added tests to cover my changes.
[x] All new and existing tests passed.
[x] I have reviewed at the Accessibility Practices for this feature, see: Aria Practices

Best practices

This repository uses conventional commit syntax for each commit message; note that the GitHub UI does not use this by default so be cautious when accepting suggested changes. Avoid the "Update branch" button on the pull request and opt instead for rebasing your branch against main.

Branch preview

Visual regression test results

Lighthouse scores

Category	Latest (report)	Main (report)	Branch (report)
Performance	0.99	0.99	0.99
Accessibility	1	1	1
Best Practices	1	1	1
SEO	1	0.92	0.92
PWA	1	1	1

What is this?

[Lighthouse](https://github.com/GoogleChrome/lighthouse) scores comparing the documentation site built from the PR ("Branch") to that of the production documentation site ("Latest") and the build currently on main ("Main"). Higher scores are better, but *note that the SEO scores on Netlify URLs are artifically constrained to 0.92.*

Transfer Size

Category	Latest	Main	Branch
Total	222.29 kB	210.938 kB 🏆	211.00 kB
Scripts	54.421 kB	48.603 kB 🏆	48.638 kB
Stylesheet	35.031 kB	30.394 kB 🏆	30.397 kB
Document	6.008 kB	5.29 kB 🏆	5.305 kB
Font	126.83 kB	126.651 kB 🏆	126.66 kB

Request Count

Category	Latest	Main	Branch
Total	45	45	45
Scripts	37	37	37
Stylesheet	5	5	5
Document	1	1	1
Font	2	2	2

Tachometer results

Chrome

## number-field [_permalink_](#user-content-number-field) ### basic-test | Version | Bytes | Avg Time | vs remote | vs branch | |---|---|---|---|---| | npm latest | 524 kB | 65.99ms - 67.46ms | - | faster ✔
8% - 11%
5.65ms - 7.82ms | | branch | 511 kB | 72.66ms - 74.26ms | slower ❌
8% - 12%
5.65ms - 7.82ms | - | ## slider [_permalink_](#user-content-slider) ### test-basic | Version | Bytes | Avg Time | vs remote | vs branch | |---|---|---|---|---| | npm latest | 480 kB | 73.82ms - 75.36ms | - | faster ✔
2% - 6%
1.86ms - 4.38ms | | branch | 467 kB | 76.72ms - 78.70ms | slower ❌
2% - 6%
1.86ms - 4.38ms | - |

Firefox

## number-field [_permalink_](#user-content-number-field) ### basic-test | Version | Bytes | Avg Time | vs remote | vs branch | |---|---|---|---|---| | npm latest | 524 kB | 146.53ms - 152.31ms | - | faster ✔
5% - 10%
7.67ms - 15.57ms | | branch | 511 kB | 158.34ms - 163.74ms | slower ❌
5% - 11%
7.67ms - 15.57ms | - | ## slider [_permalink_](#user-content-slider) ### test-basic | Version | Bytes | Avg Time | vs remote | vs branch | |---|---|---|---|---| | npm latest | 480 kB | 162.14ms - 169.22ms | - | unsure 🔍
-6% - +0%
-9.53ms - +0.09ms | | branch | 467 kB | 167.16ms - 173.64ms | unsure 🔍
-0% - +6%
-0.09ms - +9.53ms | - |

adobe / spectrum-web-components