Prepare to release version v26.8.1

[github-actions]

Update the version number for releasing the latest version of Quark.
In this version, the following changes will be included.

• Fix README malware report links ev-flow/quark-engine#942
• fix: validate default rule path only when used ev-flow/quark-engine#937
• Add Quark malware analysis report for AhRat ev-flow/quark-engine#934
• Bump pip from 26.1 to 26.1.2 ev-flow/quark-engine#951
• fix: include interfaces in superclass relationships ev-flow/quark-engine#953
• feat: add dependency-update PR validator skill ev-flow/quark-engine#932