Conduct a11y audit of ILN

[joshblack]

We've gotten some feedback from our internal a11y experts that ILN is failing basic a11y requirements. This issue is to do the following:

• [x] Conduct the initial a11y audit to find initial problems with the component
  • [ ] Verify with an a11y expert
• [ ] Perform initial implementation of fixes for the a11y violations
• [ ] Verify update actually addresses a11y violations reported in the initial audit

[marijohannessen]

Tracking this in https://github.com/carbon-design-system/carbon-addons-cloud/issues/26