Adding a11y rules to TSlint

[bhavyarm]

Contains changes to package.json and tslint.yaml for a11y rules from https://www.npmjs.com/package/tslint-microsoft-contrib

Please note I won't be merging this PR till these PRs are in:

• 1. Fixing a11y errors in querybar and suggestion_component Fixing a11y errors in querybar and suggestion_component #26892
• 2. Make space selector a button Make space selector a button #26889 @timroes
• 3. Fixing a11y errors in waffle_node_type_switcher Fixing a11y errors in waffle_node_type_switcher #26895
• 4. Fixing a11y errors in basic_login_form.tsx and edit_role_page.tsx Fixing a11y errors in basic_login_form.tsx and edit_role_page.tsx #26902
• 5. Fix a11y error in vis_type_icon.tsx Fix a11y error in vis_type_icon.tsx #26906
• 6. Adding the missing alt tag for waffle node type switcher svgs Adding the missing alt tag for waffle node type switcher svgs #27070
  (Needed both alt and presentation)

[elasticmachine]

💔 Build Failed

• continuous-integration/kibana-ci/pull-request

[bhavyarm]

This was raised as an act of desperation. The parent PR is all green and waiting for reviews. Closing it. Thanks!