Accessibility improvements

[DanielRosenwasser]

We have an internal accessibility team at Microsoft which has been able to point out the following issues

• TypeScriptLang.org_Community_AI4W: "H1" Heading level tag is not defined in the page.
• TypeScriptLang.org_Index_AI4W:Ensures aria-hidden elements do not contain focusable elements (#playground-samples-popover)
• TypeScriptLang.org_Tools_Playground_AI4W: Ensures that lists are structured correctly (#compiler-options-dropdown)
• TypeScriptLang.org_Tools_Playground_AI4W: Ensures elements with an ARIA role that require child roles contain them (ol[role="tablist"])
• TypeScriptLang.org_Tools_Playground_AI4W: Ensures elements with an ARIA role that require parent roles are contained by them (.selected.section-name.button)
• TypeScriptLang.org_Tools_Playground_AI4W: Ensures every id attribute value of active elements is unique (div:nth-child(1))
• TypeScriptLang.org_Tools_Playground_AI4W: Ensures <li> elements are used semantically (.active:nth-child(8))
• TypeScriptLang.org_Documentation_Get Started_AI4W: Ensures the contrast between foreground and background colors meets WCAG 2 AA contrast ratio thresholds (span:nth-child(3))
• TypeScriptLang.org_Documentation_Handbook_AI4W: Heading level tag is incorrectly defined in the page.
• TypeScriptLang.org_Documentation_Handbook_Keyboard: on High Contrast mode the focus is not visible on which topic we are under "On this Page"
• TypeScriptLang.org_Documentation_Handbook_Focus Order: Keyboard Focus is going on "like this page" which is incorrect focus order
• TypeScriptLang.org_Documentation_Handbook_Focus Visible: Keyboard Focus is not visible when it reaches to "like the page" and "dislike the page"
• TypeScriptLang.org-Web-Update Accessibility Conformance Documentation
• TypeScript website _Index_Reflow: In reflow some controls are missing in the navigation bar(Download, Documentation, Handbook, Playground)

[orta]

TypeScript website _Index_Reflow: In reflow some controls are missing in the navigation bar(Download, Documentation, Handbook, Playground)

Is intentional those links are still accessible through other methods, they're just available quicker when there's space