feat(tests): integrate Playwright and Vitest for testing, add CI pipeline, and update dependencies

- Added Playwright configuration for end-to-end testing.
- Integrated Vitest for unit testing with setup files.
- Updated package.json scripts for testing commands.
- Created CI pipeline for automated testing and builds.
- Added various test cases for components and pages.
- Updated .gitignore to exclude Playwright and coverage.
- Enhanced ModsList component with additional class for styling.

src/tests/components/ButtonCard.test.ts

@@ -0,0 +1,47 @@
+import { experimental_AstroContainer as AstroContainer } from 'astro/container'
+import { beforeEach, describe, expect, it } from 'vitest'
+import ButtonCard from '~/components/download/ButtonCard.astro'
+
+describe('<ButtonCard />', () => {
+  let container: Awaited<ReturnType<typeof AstroContainer.create>>
+  beforeEach(async () => {
+    container = await AstroContainer.create()
+  })
+
+  it('renders with required props', async () => {
+    const result = await container.renderToString(ButtonCard, {
+      props: {
+        label: 'Download',
+        href: '/download',
+      },
+    })
+    expect(result).toContain('Download')
+    expect(result).toContain('href="/download"')
+    expect(result).not.toContain('Show SHA-256')
+  })
+
+  it('renders with checksum', async () => {
+    const result = await container.renderToString(ButtonCard, {
+      props: {
+        label: 'Download',
+        href: '/download',
+        checksum: 'sha256sum',
+      },
+    })
+    expect(result).toContain('Show SHA-256')
+    expect(result).toContain('sha256sum')
+    expect(result).toContain('Copy')
+  })
+
+  it('renders with variant', async () => {
+    const result = await container.renderToString(ButtonCard, {
+      props: {
+        label: 'Download',
+        href: '/download',
+        variant: 'flathub',
+      },
+    })
+    expect(result).toContain('Download')
+    expect(result).toContain('Beta')
+  })
+})