Case sensitivity

[nvsajeeva]

It looks like contribcard currently considers the case of a GitHub handle. This causes problems when integrated with CertDirectory user profiles.

For example:

✅ Works: User 1 profile

❌ Broken: User 2 profile

Other integrations (like DevStats score and GitHub heatmap) work fine for the second user, since GitHub itself ignores case.

Proposed fix
Update contribcard to handle GitHub usernames in a case-insensitive manner.
i.e
Both of the following calls should return the card
https://contribcard.cncf.io/galphaa
https://contribcard.cncf.io/Galphaa