Add references to Mock API Template library contributing posts on the contributing page

[oleg-nenashev]

Proposal

Recently we published two articles about creating and contributing to Mock API Templates:

• https://www.wiremock.io/post/how-to-contributing-to-wiremock-api-templates-library
• https://www.wiremock.io/post/creating-mock-api-templates-from-openapi

It would be nice if the contributing page includes those articles too

References

• https://library.wiremock.org/how-to-contribute/
• doc: add the how-to guide to the contributing guide api-template-library#25 - similar patch