Improve documentation links and consistency

### Description
While going through the documentation, I noticed a few small issues related to links and consistency that could affect readability and long-term maintenance.

### Observations
1. The Gateway API CRD installation uses a hardcoded Git commit reference, which may become outdated over time
2. The relative link `develop-with-kind/` might not always resolve correctly depending on routing
3. Some naming inconsistencies like "istio" instead of "Istio"

### Suggested Improvements
- Replace hardcoded commit references with a stable or maintained link
- Update relative links to clearer or more reliable paths
- Maintain consistent naming for technologies across the docs

### Impact
These changes would make the documentation more reliable and slightly improve the experience for new users and contributors.