Installs react router compat package to incrementally upgrade to v6

[benhammondmusic]

Description and Motivation

Incremental migration from react-router-dom v5 to v6 following https://github.com/remix-run/react-router/discussions/8753

• installs compat package that runs both v5 and v6 apis
• migrates WHAT IS HEALTH EQUITY and NEWS sub routes over to v6 via the compat package
• once the whole app is via the compat package using v6 apis we can remove it and the components will work perfectly with v6
• extracts the text/icon from the HetTextArrowLink component, since we are using it on cards where the whole thing is linked, causing issues with nested <a>s. This way if we want the arrow on a larger linked item we can, or used on its own with the linking features and animation on hover

Has this been tested? How?

tests passing after updating their test routers to use compat as well

Types of changes

(leave all that apply)

• Bug fix
• Refactor / chore

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