Add keywords to Salt DS Assets library

[pseys]

To improve the findability/searchability of design assets within Salt, keywords should be added to the descriptions of icons and country symbols within the Salt DS Assets library.

For example, the accessible icon has been used as a test by adding the descriptive terms 'wheelchair', 'disability', and 'accessibility'. In addition the following terms could also be added:

• 'ADA', 'WCAG', and 'A11Y'
• The solid variant name accessible-solid as it is not currently searchable
• The component name format Accessible and AccessibleSolid