fix: Nav link state for screen readers

[SatyamSetia]

Describe your changes

Added aria-current to anchor tags in NavItem component. if link is active then, set the value of aria-current to be "page" else set it to false.

Link to issue

Closes #343

Checklist before requesting a review

• I have performed a self-review of my code.
• Followed the repository's Contributing Guidelines.
• I ran the app and tested it locally to verify that it works as expected.
• I have checked my code with an automatic accessibility tool such as Axe Dev Tools or Wave
  and it shows no errors.

[SatyamSetia]

Hey, @EmmaDawsonDev
Requesting your review on this PR whenever you get time.

[EmmaDawsonDev]

Looks great! Thanks so much for your help!