fix: make corner SVGs unfocusable in IE

[DeoJin]

Summary

• add ocusable="false" to the shipped corner SVG assets
• update every inline demo snippet in index.html to include the same accessibility fix
• keep the change scoped to the decorative SVG markup used inside links

Testing

• regex sanity check: index.html now has 21 tags and 21 ocusable="false" attributes
• verified both exported SVG assets contain ocusable="false"

Fixes #45