High priority visual accessibility issues

[peterychang]

Reference spreadsheet: https://microsoft.sharepoint.com/:x:/t/AIRAccessibilityMetrics/EUKpsd8MzCJNmjkEegC3Y7sBTkiccRpyb21CUVIGXFNM4w?e=Q85tsc&CID=32e3a4f7-b13e-3241-96bd-e728ef558053

Issues:

• (6) Luminosity contrast ratio of focus indicator on 'Venv' control is less than 3:1.
• (14) Ensures the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds
• (20) "Only color is used to indicate the focus indicator on the 'Venv', and 'conda' Tab controls."
• (33) In 400% zoom mode, horizontal bar is appearing.
• (46) In high contrast mode, keyboard focus indicator is not visible on Left &right navigation pane, Home icon, Core and tab controls 'Venv' and 'Condo'.
• (51) Luminosity contrast ratio of back and close control is less than 3:1.
• (54) Luminosity ratio for the Back to top control is less than the required ratio 4.5:1.
• (55) In high contrast mode, keyboard focus indicator is not visible on the controls appearing in On this page section.
• (56) Users are not able to differentiate between selected and not selected state of links present in On this page section in high contrast mode.