chore: migrate GH issue template to issue form

See https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository#creating-issue-forms

.github/ISSUE_TEMPLATE/feature-request.yml

@@ -0,0 +1,28 @@
+name: 🚀 Feature request
+description: Suggest an improvement.
+title: Suggest an improvement
+labels: [proposal]
+assignees: []
+body:
+- type: checkboxes
+  attributes:
+  label: Prerequisites
+  description: Take a minute to help our open source contributors.
+  options:
+  - label: I have [searched](https://github.com/wowchemy/wowchemy-hugo-themes/issues?q=is%3Aissue) for duplicate or closed feature requests
+  - label: I am mindful of the project [scope](https://github.com/wowchemy/wowchemy-hugo-themes/blob/main/.github/contributing.md#scope)
+  required: true
+- type: textarea
+  id: proposal
+  attributes:
+  label: Proposal
+  description: Provide detailed information for what we should add, including relevant links to screenshots, code, or live demos whenever possible.
+  validations:
+  required: true
+- type: textarea
+  id: motivation
+  attributes:
+  label: Motivation and context
+  description: Tell us why this change is needed or helpful, and what problems it may help solve.
+  validations:
+  required: true