Release 2.6.0

[pwtyler]

Feature Updates

• Adds is_solr_query filter ([CMSP-486] Add is_solr_query filter #588)
• Fixes custom schema file path for Composer Managed and other non-standard uploads directories. ([BUGS-8883] Fix custom schema path for WPCM sites #637)
• Adds filter solr_power_customer_schema_file_path to specify an alternative custom schema.xml file. ([BUGS-8883] Fix custom schema path for WPCM sites #637)

Housekeeping

• Updates sass package in grunt build step (chore: Replace deprecated node-sass package #641)
• CODEOWNERS ([SITE-1547] Update CODEOWNERS for new team names #629)
• Introduces build-tag-release from plugin release actions (Use build-tag-release action #646)

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Closes https://getpantheon.atlassian.net/browse/BUGS-8883