fix(theme-common): isSamePath should be case-insensitive

[slorber]

Motivation

Sometimes the user has a filename like Capitalized.md leading to a slug with some uppercase chars such as /docs/Capitalized

But this URL is often normalized to /docs/capitalized by CDN/hosts and then when we try to match the 2 paths we consider they are different.

This leads to subtle UX issues such as:

• empty breadcrumb
• bad navbar item highlighting
• bad sidebar category/items highlighting

The helper function isSamePath should be case-insensitive to fix it.

Have you read the Contributing Guidelines on pull requests?

yes

Test Plan

tests + dogfood

[netlify]

✔️ [V2]

🔨 Explore the source changes: ece6ea2

🔍 Inspect the deploy log: https://app.netlify.com/sites/docusaurus-2/deploys/6218dd4278415a00084e488f

😎 Browse the preview: https://deploy-preview-6758--docusaurus-2.netlify.app

[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🔴 Performance	47
🟢 Accessibility	100
🟢 Best practices	92
🟢 SEO	100
🟢 PWA	90

Lighthouse ran on https://deploy-preview-6758--docusaurus-2.netlify.app/

[github-actions]

Size Change: +669 B (0%)

Total Size: 783 kB

Filename	Size	Change
website/.docusaurus/globalData.json	48.3 kB	+174 B (0%)
website/build/assets/js/main.********.js	592 kB	+495 B (0%)

ℹ️ View Unchanged

Filename	Size
website/build/assets/css/styles.********.css	106 kB
website/build/index.html	37.6 kB

_{compressed-size-action}