Doc: Standard pattern for GitHub link doesn't resolve correctly

[karenzone]

Page: https://www.elastic.co/docs/reference/logstash/plugins/plugins-filters-elastic_integration#_getting_help_137

The "Get Help" section is populated by an included header file that uses variables to present the GitHub path. The pattern breaks for filter-elastic_integration because this plugin doesn't live in the logstash-plugins GitHub org. This will likely require a manual override.

Description of fixes

• Add new non-standard header file
• Update filter-elstic_integration file to use new non-standard header

Fixes needed

• Generated output in logstash-docs:
  • Stack-versioned plugins
    • main: Add header for non-standard repo logstash-docs#1840
    • 9.0: Add header for non-standard repo 9.0 logstash-docs#1848
  • VPR: VPR: Use non-standard header for intg filter logstash-docs#1850
• MD files in logstash-docs-md:
  • LSR: https://github.com/elastic/logstash-docs-md/pull/18
  • VPR: https://github.com/elastic/logstash-docs-md/pull/18
• Logstash Reference in (logstash and logstash-docs):
  • 8.19:
    • Doc: Add non-standard header file logstash#17600
    • Use non-standard header 8.18 logstash-docs#1854
  • 8.18:
    • [8.18] (backport #17600) Doc: Add non-standard header file logstash#17609
    • Use non-standard header 8.18 logstash-docs#1854
  • 8.17:
    • [8.17] (backport #17600) Doc: Add non-standard header file logstash#17610
    • Use non-standard header 8.17 logstash-docs#1855
• Doc source in logstash-filter-elastic_integration: Doc: Update plugin to use nonstandard header #297
  • [8.17] (backport #297) Doc: Update plugin to use nonstandard header #298
  • [8.18] (backport #297) Doc: Update plugin to use nonstandard header #299
  • [8.19] (backport #297) Doc: Update plugin to use nonstandard header #300
  • [9.0] (backport #297) Doc: Update plugin to use nonstandard header #301

And... to catch pages that came through after we started this effort:

• auto generated update of versioned plugin documentation with corrections logstash-docs#1852