React-markdown: Upgrade to version 8.0.7 to be compatible with rollup

Updated imports and config to support new version

J=CLIP-1321
TEST=auto|manual

Use `npm run test` to run test suite and check that `npm run build` returns no errors
Performed manual testing on test-site to ensure functionality remained the same

jest.config.json

@@ -12,7 +12,8 @@
   "clearMocks": true,
   "testMatch": ["<rootDir>/tests/**/*.(test).ts(x)?"],
   "moduleNameMapper": {
-    "\\.(css|scss|less)$": "<rootDir>/tests/__utils__/style-mock.ts"
+    "\\.(css|scss|less)$": "<rootDir>/tests/__utils__/style-mock.ts",
+    "react-markdown": "<rootDir>/node_modules/react-markdown/react-markdown.min.js"
   },
   "setupFilesAfterEnv": ["<rootDir>/tests/__setup__/setup.js"]
 }