changeset: add changesets for UrlReader addition

.changeset/create-app-url-reader-update.md

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+---
+'example-backend': patch
+'@backstage/create-app': patch
+---
+
+Bump @backstage/catalog-backend and pass the now required UrlReader interface to the plugin

.changeset/new-url-reader.md

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+---
+'@backstage/backend-common': patch
+---
+
+Added new UrlReader interface for reading opaque data from URLs with different providers.
+
+This new URL reading system is intended as a replacement for the various integrations towards
+external systems in the catalog, scaffolder, and techdocs. It is configured via a new top-level
+config section called 'integrations'.
+
+Along with the UrlReader interface is a new UrlReaders class, which exposes static factory
+methods for instantiating readers that can read from many different integrations simultaneously.

.changeset/url-reader-processor.md

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+---
+'@backstage/plugin-catalog-backend': minor
+---
+
+The catalog backend UrlReaderProcessor now uses a UrlReader from @backstage/backend-common, which must now be supplied to the constructor.