Big upgrade for our token-directory repo.

1. We now generate a index/index.json file before every commit, which is a singular file that remote indexers can fetch, and from here will be able to query all other contents. It also includes a checksum of the file so indexers can keep track if the contents have changed or not. It also performs validity checks of JSON and also chainIds.
2. New index/deprecated.json file which is manually maintained, and the idea is you can list any chain name folder in this list, and it will be labeled as deprecated in the index/index.json file.
3. New index/external.json file which is a manually maintained list of external token lists, which can be indexed. Advantage is this is a dynamic list, and will be picked up by external indexers on-demand.
4. We introduce new pnpm reindex which triggers pre-commit to generate the master index/index.json file
5. We introduce new pnpm sync-external which will download the contents from remote index/external.json files and persist them in our local directory in index/_external and also added to the master index/index.json file