IJM: separate "editorial policy" and "author guidelines"

[sianroderick]

On the About page (https://microsimulation.pub/about), "editorial policy" and "author guidelines" are combined on one page. IJM would like to separate these two sections onto different pages, and have an additional like in the horizontal menu.

[sianroderick]

Awaiting confirmation of text and menu label

[sianroderick]

The new page should be titled "Submission guidelines".

Text on this page should be the first two sections that currently appear on: https://microsimulation.pub/about/editorial-policy

• Submissions
• Tables, Figures and Algorithms

That text can then be removed from the "Editorial policy" page, such that the page starts with the "Fees" section.