chore(main): release 0.26.0

[release-please[bot]]

:robot: I have created a release beep boop

0.26.0 (2023-05-10)

Features

• Add extra_opts for C# proto generation (#156) (d412924)

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[release-please[bot]]

:robot: Release is at https://github.com/googleapis/rules_gapic/releases/tag/v0.26.0 :sunflower: