fix(CI): mkdir -p for assets

[hgw77]

Summary

this will create the path for assets if not existing

• I have performed a self-review of my code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have made corresponding changes to the documentation (if applicable).
• My changes generate no new warnings or errors.

[andypf]

LGTM