"To preview theme, visit: " should be URL encoded

[brycekirk]

Description

The preview theme link that Hubspot generates fails if the theme name has a space in it since it isn't URL encoded.

Steps to reproduce

hs watch a theme that isn't the published one and a preview link appears: https://app.hubspot.com/theme-previewer/{account number}/edit/{theme name}

Expected behavior

The theme name should be URL encoded, ie spaces converted to %20, etc,