* Explain data crawler structure
* Add documentation for data and feature
* Update scripts/data_collector/yahoo/README.md
Co-authored-by: you-n-g <you-n-g@users.noreply.github.com>
* Remove some confusing wording
* Add third party data source
* Fix command typo
* Update commands
Co-authored-by: you-n-g <you-n-g@users.noreply.github.com>
* Fix high-freq data name from `yahoo_cn_1min` to `cn_data_1min`
* re-format example data names using `qlib_{region}_{feq}`, e.g. qlib_cn_1d
* re-format example data names using `{region}_{feq}`, e.g. us_1d and cn_1min
* keep using for 1day data, and change 1min data to