ci: ignore URLs in spelling checks (#659)

# Description

Words from
2698cc0
pushed to main branch directly used to fail #658.

Ignoring URLs according to the
[docs](https://docs.check-spelling.dev/Configuration-Examples:-patterns).

The fix was tested in the affected PR:
[before](https://github.com/a2aproject/a2a-python/actions/runs/21582994306),
[after](https://github.com/a2aproject/a2a-python/actions/runs/21584577892).

Author: ishymko

.github/actions/spelling/patterns.txt

@@ -0,0 +1,2 @@
+# Ignore URLs
+https?://\S+