Add alignment controls for title and caption in panel output

[dusktreader]

Proposed Enhancement

I propose that options are added to align the title and caption in panel output.

Background

I've made a lot of use of these alignment options while use rich in code. In general, I find left aligning titles more useful than center alignment.

Changes

I think adding the following options would provide intuitive control of alignment

• --title-left
• --title-right
• --caption-left
• --caption-right