Feature: Short link/vanity URL creator

### As a Public Information Officer, I want to be able to create a descriptive but succinct and memorable URL so that I can use it for a campaign or on advertising.

**Is your feature request related to a problem? Please describe.**
During our microresearch, we learned that one of the (many) reasons why microsite owners prefer a microsite is that they have an easy URL to point to on print and digital campaigns and ads. Instead of splitting audiences on a new domain, how might we allow departments to host their content on austin.gov but still have bespoke URLs to work for their purposes?

**Describe the solution you'd like**
A feature in Joplin that allows a user to author and create a short URL for a page.

**Describe alternatives you've considered**
*A clear and concise description of any alternative solutions or features you've considered.*

**Additional context**
This emerged from our microsite research:
[Final presentation](https://docs.google.com/presentation/d/1YYubvvJGXMoWgUuO7_6ACQIpnZUH6IY6-jNe3GDJVfg/edit?usp=sharing)
[Microresearch overview](https://docs.google.com/document/d/1hi8VYR0sB1Of-CdVAMfFemh0pHtONjCVaxls-IGk7sk/edit?usp=sharing)