Fix broken links in docs #278

We now have automated testing of links and image paths.

The tests are kicking up these issues:

• SUBFAILED[Broken heading link: /pages/support/submission/submission-settings.html -> System settings #submission-settings] (i=20) tests/test_accessibility.py::test_all_pages[chromium] - assert False
• SUBFAILED[Broken image: /pages/support/about/contributing-guide.html -> The words "cat" and "dog" appear next to bullet points, and descriptions appear underneath each word ./images/lists-with-definitions.png] (i=26) tests/test_accessibility.py::test_all_pages[chromium] - playwright._impl._errors.Error: APIRequestContext.get: socket hang up
• SUBFAILED[Link to duplicate headings: /pages/support/about/janeway-styleguide.html -> Language and grammar #language-and-grammar] (i=28) tests/test_accessibility.py::test_all_pages[chromium] - assert False
• SUBFAILED[Link to duplicate headings: /pages/support/about/janeway-styleguide.html -> Language and grammar section #language-and-grammar] (i=28) tests/test_accessibility.py::test_all_pages[chromium] - assert False
• SUBFAILED[Link to duplicate headings: /pages/support/about/janeway-styleguide.html -> Language and grammar section #language-and-grammar] (i=28) tests/test_accessibility.py::test_all_pages[chromium] - assert False
• SUBFAILED[Link to duplicate headings: /pages/support/repository/moderator-guide.html -> Controls section #controls] (i=42) tests/test_accessibility.py::test_all_pages[chromium] - assert False
• SUBFAILED[Link to duplicate headings: /pages/support/repository/moderator-guide.html -> Controls section #controls] (i=42) tests/test_accessibility.py::test_all_pages[chromium] - assert False
• SUBFAILED[Broken heading link: /pages/support/issues-volumes-and-collections/issues-and-volumes.html -> Creating and editing issues #creating-and-editing-issues] (i=62) tests/test_accessibility.py::test_all_pages[chromium] - assert False
• SUBFAILED[Broken image: /pages/support/press-management/index.html -> The Press Manager page ../../images/press-manager.png] (i=100) tests/test_accessibility.py::test_all_pages[chromium] - playwright._impl._errors.Error: APIRequestContext.get: socket hang up
• SUBFAILED[Broken heading link: /pages/support/guides/account-troubleshooting.html -> Activating accounts ../accounts-and-roles/activating-accounts#activating-accounts-1] (i=105) tests/test_accessibility.py::test_all_pages[chromium] - assert False