Document Snowflake source support

[kwannoel]

Context

Slack thread: Request to document this feature

A docs request was raised for the Snowflake source feature added in risingwave#23988.

Problem

Snowflake source support is available in RisingWave, but there is no dedicated documentation explaining how to set it up and use it. This creates a gap for users who need source-side guidance (as opposed to sink-only workflows), including required configuration, setup steps, and known constraints.

Suggested Fix

• Add a dedicated Snowflake Source documentation page under integrations/sources.
• Document prerequisites and authentication/connection requirements.
• Include required connector properties and configuration examples.
• Provide an end-to-end SQL walkthrough (for example: CREATE CONNECTION and CREATE SOURCE) plus a quick validation query.
• Clarify current limitations, compatibility notes, and feature availability/licensing expectations.
• Add cross-links from related Snowflake and connector overview pages to improve discoverability.

Existing Documentation

• reference/rw-flink-feature-comparison.mdx
• get-started/premium-features.mdx
• changelog/product-lifecycle.mdx
• changelog/release-support-policy.mdx
• integrations/destinations/bigquery.mdx

Related docs PRs:

• docs: add pulsar.read_compacted option for compacted topic consumption
• docs: add best practices for unnest function with performance explanations
• Document watermark TTL
• Document: add key-pair authentication for Snowflake v2 sink
• Document: add Redis Stream sink

Codebase References

Related PRs in risingwave:

• feat: add a config to control whether state table vnode prunning is enabled
• feat: risectl command to force change Source Connector Props
• feat: support ALTER CONNECTION CONNECTOR WITH
• chore(deps): Bump quick-xml from 0.38.3 to 0.39.0
• feat: snowflake source support

Source files:

• risingwavelabs/risingwave/src/license/src/feature.rs
• risingwavelabs/risingwave/docs/dev/src/contributing.md
• risingwavelabs/risingwave/docs/rustdoc/rust.css
• risingwavelabs/risingwave/src/error/src/code.rs
• risingwavelabs/risingwave/README.md