[DOCS] Update catalog docs to show automatic catalog syncs to Snowflake and Glue

[sagarlakshmipathy]

Important Read

https://github.com/apache/incubator-xtable/issues/548

What is the purpose of the pull request

• Update Glue and Snowflake docs to show better catalog sync methods for iceberg tables

Brief change log

• Updated Glue catalog doc
• Updated Snowflake integration doc

Verify this pull request

• Trivial docs work
• Checked with npm start locally