Add editable page for gym

[NedReid]

AC1: WHEN: I navigate to "Facilities" in the header THEN I should see a link to "Gym" in the subheader

AC2: WHEN: I navigate to the gym page THEN I should see a page for the college gym with the header "Gym"

AC3: WHEN: I have the "gym" editable permission THEN I should see an edit icon the top-right, that allows me to edit the page.

Dan and Arman have given us a list of extra pages to add. This is the first one. It's an "editable" type, meaning that all we need to do is make a blank page. Writing the content of the page is not part of this ticket.

Technical elaboration

• When working on the site, I made a class called "editables". These are very simply a type of page that is static to most people, but certain people have permission to edit the page in a WYSIWYG editor.
• This makes this ticket actually extremely straightforward. This ticket can be done completely in the frontend.
• All you need to do essentially is copy frontend/components/static/Finance.jsx, but change the variables and content so it's "gym" instead.
• Then, you need to go to App.jsx and make a route to the gym page
• Finally, you need to go to global/menuItems.jsx and add the gym to the header
• to test that the editable works, make a page called "gym" on the admin page and add your username to it, then navigate back to the gym page.

[NedReid]

This is actually a really simple frontend ticket, even though it's actually adding an entire new page! Pretty okay one to take on!