feat: add SelectPreference component

[AprilSylph]

Description

• relates to refactor: use Web Components to render features in the control panel #1831
• relates to feat: add CheckboxPreference component #2055
• relates to feat: add TextPreference component #2075
• relates to feat: add TextAreaPreference component #2086
• relates to feat: add ColorPreference component #2089

Creates a SelectPreferenceElement class and SelectPreference shorthand function, for rendering colour-type preferences.

Like previous preference components, this PR does not implement any usages of the component, just the component itself.

This one was fun, because I found out that setting HTMLSelectElement.value does actually work, provided it matches the value of one of the <option> elements. I've opted to keep the code simple by leveraging this, which does come at the cost of component instances needing to set options before setting its own value, but I think that's fine—the JSdoc already says that value must match one of the options.

Testing steps

1. Pull this branch locally
2. Apply this patch: select-preference.patch
3. Load the modified addon
4. Open the XKit control panel and enable Vanilla Audio
   • Expected result: The "Default Volume" preference renders without issue
   • Expected result: The "Default Volume" preference renders showing 100% selected, which is notably not the first option in the list
5. Change a select-type preference in any feature
   • Expected result: The changed preference value is reflected in the Backup tab
6. Close and reopen the XKit control panel
   • Expected result: Any changed select-type preferences render showing their saved value selected, instead of their default