Collection View - Deposits page: "major" accessibility issues that may not need design

[ndushay]

From https://docs.google.com/spreadsheets/d/1Fs5sY1zgpovWVdHMqpJWRu2Zvyr53jw7, here are "major" accessibility issues for the Dashboard page that we can fix without design changes. (Note: Mike addressed accessibility level A and AA problems noted by the SiteImprove, WAVE and Axe browser plugins in PRs #3161)

Note that solutions may be suggested in https://docs.google.com/spreadsheets/d/1Fs5sY1zgpovWVdHMqpJWRu2Zvyr53jw7.

These can be separate PRs, and/or split into separate tickets.

• Ensure sortable column headers include proper text alternatives. Sortable column headers do not communicate if they are sortable and the current sorted state of any sorted header cells.
• There are multiple <h5> instances with an id="content-type-prompt" present. (see PR Improve accessibility for welcome/home page and dashboard #3159 for how Mike changed this for dashboard). See same for Collection View - Collection Settings page Collection View - Collection Settings page: "major" accessibility issues that may not need design #3175
• The "Cite" button is repeated multiple times; form field labels should be unique. See Cite buttons do not have unique IDs #3188
• Search field - A placeholder attribute is used in place of an input labels for the Search field. Placeholder values that disappear when a value is entered are not valid labels.
• title - There are headings that are only styled to look like headings but are not marked as such in HTML. The visible heading "A Test Collection for Honors Theses Revised" is not marked up as a heading.
• In the pagination section, the current page is conveyed visually, but not programmatically. The next link is just an angle and announced as " single right pointing angle quotation mark" to screen readers. Custom controls should provide textual name (link or button label, form label text) and state information (i.e. "expanded", "collapsed", selected, current). (Possibly fixed by Improve accessibility for collections pages #3161. Same problem in Deposit form: "major" accessibility issues that may not need design #3170)
• The link to move to the next page is the ">" character and is announced as "single right pointing angle quotation mark" by a screen reader.
• When text is entered in the Search field, the table automatically updates without any indication provided to assistive technology users.
• The focus order of elements on the page does not match the expected focus order. When a sortable column is sorted in the table, focus is moved away from the control.
• (level Minor) The modal dialogs each have <h5> headings instead of <h2>; structural markup should accurately communicate the heading level.
• (level Minor) The three links "Collection details," "Collection settings," and "Deposits" are structured as tabs (role="tab"), but they are not three different areas of content on the same page. They are actually three different pages.
• (level Minor). There are multiple nav elements present on the page and they do not have labels. HTML landmarks (aside, nav, etc.) should have unique accessible names as required when two or more landmark elements of the same type are present.