Add value ranges and types for PD configuration items

Feature Request

Is your feature request related to a problem? Please describe:

The users of the document PD Configuration File might need to know the value ranges and types of certain configuration items. However, only some of these configuration items in this document have value range and type information.

Describe the feature you'd like:

Contribute to TiDB documentation by providing value range and type information for the following configuration items. This document is in the pingcap/docs repository. To contribute to this document, follow the TiDB Documentation Contributing Guide. See https://github.com/pingcap/docs/pull/5530 for example.

If you have already created a PR for one or more items below, please tick the corresponding box(es) and provide the PR link at the end of the line.

• max-size
• max-days
• max-backups
• max-merge-region-size
• max-merge-region-keys
• patrol-region-interval
• split-merge-interval
• max-snapshot-count
• max-pending-peer-count
• max-store-down-time
• leader-schedule-limit
• region-schedule-limit
• replica-schedule-limit
• merge-schedule-limit
• high-space-ratio
• low-space-ratio
• store-balance-rate https://github.com/pingcap/docs/pull/5530

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy: