Add `tsconfig.json` to all examples

[maoueh]

Now that typings works properly with graph-ts @ 0.23.1, all examples should be using a proper tsconfig.json to get typings resolve properly.

Content:

{
    "extends": "@graphprotocol/graph-ts/types/tsconfig.base.json",
    "include": ["src"]
}

See https://github.com/graphprotocol/example-subgraph/blob/near-blocks-example/tsconfig.json