Document Pulsar topicsPattern regex subscriptions

[jslatten]

Thank you for helping make the Dapr documentation better!

Please follow this checklist before submitting:

• Commits are signed with Developer Certificate of Origin (DCO - learn more)
• Read the contribution guide
• Commands include options for Linux, MacOS, and Windows within tabpane
• New file and folder names are globally unique
• Page references use shortcodes instead of markdown or URL links
• Images use HTML style and have alternative text
• Places where multiple code/command options are given have tabpane

Description

Documents the new topicsPattern and autoDiscoveryPeriod metadata fields on the Apache Pulsar pub/sub component, which add support for subscribing to multiple topics within a tenant/namespace by regular expression (with Pulsar auto-discovering newly created matching topics).

Changes to reference/components-reference/supported-pubsub/setup-pulsar.md:

• Two new rows in the Spec metadata fields table: topicsPattern and autoDiscoveryPeriod.
• A new Subscribe to multiple topics with a pattern section explaining the behavior, scoping (tenant/namespace), regex (not glob) semantics, auto-discovery, concrete-topic delivery, and the schema-validation caveat, with a YAML example.

This is the documentation counterpart to the component implementation in dapr/components-contrib (PR linked below), as required by the components-contrib contribution process.

Issue reference

Relates to dapr/components-contrib#2566
Implementation PR: dapr/components-contrib#4422