[MGPG-130] Update sigstore extension to ".sigstore.json"

[jira-importer]

Appu Goundan opened MGPG-130 and commented

Sigstore uses ".sigstore.json" extensions for all newer versions of the clients (maven, gradle, other languages). 

An update to https://github.com/apache/maven-gpg-plugin/blob/master/src/main/java/org/apache/maven/plugins/gpg/FilesCollector.java#L44-L45 should be sufficient.

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This issue is a sub-task of MGPG-95

Issue Links:

• MRESOLVER-680 Disable checksum by default for .sigstore.json as well

Remote Links:

• GitHub Pull Request #109