message: Add missing links to ff.com docs
  has some broken links. Fixing them.
diff: @@ -110,3 +110,8 @@ Typical scenarios require the connected clients to "agree" on some course of act
  - Import data from an external source. (Multiple clients doing this could lead to duplicate data.)
  - Upgrade a data schema. (All clients agree to simultaneously make the change.)
  +
  +<!-- Links -->
  +[SharedMap]: https://fluidframework.com/docs/apis/map/sharedmap/
  +[SharedDirectory]: https://fluidframework.com/docs/apis/map/shareddirectory/
  +[SharedString]: https://fluidframework.com/docs/apis/sequence/sharedstring/
  