first cut at API checking

The API files are empty in this commit, and will hopefully be
filled in in later (to be squashed or amended) commits.

.github/workflows/check-api.yml

@@ -54,7 +54,7 @@ jobs:
           chmod +x print-api
 
       # print-api needs environment files. It also doesn't make a lot of sense to use the cached builds, sadly,
-      # since they're special in different ways (bootstrap and validate) and we want a vanulla build. And there
+      # since they're special in different ways (bootstrap and validate) and we want a vanilla build. And there
       # isn't enough cache space to make a third cache, even though this is a very limited build.
       - name: Build Cabal with environment files
         shell: bash