feat: add initial draft of a new pattern 'walk the InnerSource talk'

[deveaud-m]

This pattern has been collaboratively written by the team behind the social coding platform at Siemens, summarizing key lessons learned from implementing Open Source methodologies across diverse and globally distributed development teams.

This pattern emerged from discussions with @spier during FOSS Backstage 2025 and subsequent conversations in issue #799. It addresses the "dogfooding" aspect of InnerSource initiatives - a crucial concept not yet covered by existing patterns. This PR documents how we've successfully implemented this approach at Siemens.

Looking forward to your feedback about this new pattern!

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[MaineC]

This pattern sounds really nice.

We already have an example of this approach in one of our books:

https://innersourcecommons.org/documents/books/AdoptingInnerSource.pdf (check out 'leading by example') that quotes the approach at 'infrastructure based InnerSource ' in scientific literature. Feel free to add these links as references in the pattern.

[deveaud-m]

This pattern sounds really nice.

We already have an example of this approach in one of our books:

innersourcecommons.org/documents/books/AdoptingInnerSource.pdf (check out 'leading by example') that quotes the approach at 'infrastructure based InnerSource ' in scientific literature. Feel free to add these links as references in the pattern.

Thanks @MaineC for the feedback and the reference to the O'Reilly book, I added a mention of the Eurospace case-study in the pattern 065e646, let me know if this is the right place in the pattern or if I should had more details.

[spier]

LGTM

Let's get this merged, to make it easier to gather feedback from the broader InnerSource community.

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