Add aria-label attribute to tier-selector to fix accessibility error

[patdunlavey]

What does this Pull Request do?

Adds an area-label attribute to the language and speaker selector. This is the only error identified by the Web AIM accessibility checker for the transcript user interface.

How should this be tested?

Use the WAVE chrome extension to view an oral history object with a transcription present. Prior to applying this change, a "missing form label" error is flagged on the select element identified by data-header="Select languages"

After applying this code change and re-running the accessibility test on this page, the accessibility error disappears.

Additional Notes:

Does the aria-label "Transcript language and speaker selector" make sense?

• Does this change require documentation to be updated? No
• Does this change add any new dependencies? No
• Does this change require any other modifications to be made to the repository (ie. Regeneration activity, etc.)? No
• Could this change impact execution of existing code? No

Interested parties

@Natkeeran @MarcusBarnes

[MarcusBarnes]

@patdunlavey I really like this. Thank you. The Travis failure is not related to your code. We have to update our Travis checks for this repo. I'll test next week, but as this is a small change, I expect we can proceed with merging after the test.

[MarcusBarnes]

Thanks again @patdunlavey for your contribution. Much appreciated.