chore: remove npm lockfile (#771)

Removes `npm`'s `package-lock.json` file in favor of `yarn.lock`. All
the documentation tooling in CI/CD uses yarn exclusively, and so should
all the maintainers. Mixing package managers can cause inconsistencies
in dependency resolution and is better avoided.

Author: barjin

.gitignore

@@ -47,6 +47,8 @@ website/apify-shared-docspec-dump.jsonl
 website/docspec-dump.jsonl
 website/module_shortcuts.json
 website/typedoc-types*
+# npm lockfile (we use yarn)
+website/package-lock.json
 
 # Default directory for memory storage
 storage/