fix: load default css on interstitial

[2color]

Due to the way that CSS is lazy loaded, the default styles are not applied to the Interstitial page, which loads the .sans-serif class from ipfs-css rather than the overridden one in the default styles.

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works