Summary

Add the HVE Core extension (ise-hve-essentials.hve-core-all) to both .vscode/extensions.json recommendations and the .devcontainer/devcontainer.json extensions list so contributors get prompted to install it automatically. Also add a "Built with HVE Core" note to the main README.md.

Current State

• .vscode/extensions.json recommends 5 extensions (Ruff, cspell, Pylance, Python) but not HVE Core
• .devcontainer/devcontainer.json lists 30+ extensions but not HVE Core
• README.md references hve-core in prerequisites but has no visible "built with" attribution

Changes Required

1. Add "ise-hve-essentials.hve-core-all" to the recommendations array in .vscode/extensions.json
2. Add "ise-hve-essentials.hve-core-all" to the customizations.vscode.extensions array in .devcontainer/devcontainer.json
3. Add a "Built with HVE Core" note to the main README.md

Migrated from Azure-Samples/azure-nvidia-robotics-reference-architecture#414