add cursor & link-like styling to post delete button

[JakeMBauer]

This adds a couple extra bits of CSS to make the delete button stand out more as a clickable element. Preview below:

[cblgh]

thanks @JakeMBauer, i'll look at adding your additions in the next batch of work i do on cerca (probably once we shift back from the october theme!)

got some other stuff in the pipeline atm that needs to be taken care of first 👍

[cblgh]

superceded by recent theming work, thanks though!