feat: support webp format

[bubkoo]

add the webp property to the mimes object

re #326

Description

Motivation and Context

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)
• [ ] Enhancement (changes that improvement of current feature or performance)
• [ ] Refactoring (changes that neither fixes a bug nor adds a feature)
• [ ] Test Case (changes that add missing tests or correct existing tests)
• [x] Code style optimization (changes that do not affect the meaning of the code)
• [ ] Docs (changes that only update documentation)
• [ ] Chore (changes that don't modify src or test files)

Self Check before Merge

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[codecov[bot]]

Codecov Report

Base: 67.05% // Head: 67.05% // No change to project coverage :thumbsup:

Coverage data is based on head (3634676) compared to base (d9971a7). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #343 +/- ## ======================================= Coverage 67.05% 67.05% ======================================= Files 10 10 Lines 513 513 Branches 118 118 ======================================= Hits 344 344 Misses 120 120 Partials 49 49 ``` | [Impacted Files](https://codecov.io/gh/bubkoo/html-to-image/pull/343?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=%E5%B4%96) | Coverage Δ | | |---|---|---| | [src/mimes.ts](https://codecov.io/gh/bubkoo/html-to-image/pull/343/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=%E5%B4%96#diff-c3JjL21pbWVzLnRz) | `75.00% <ø> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=%E5%B4%96). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=%E5%B4%96)

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[vivcat[bot]]

:tada: This PR is included in version 1.11.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: