Adds changelog for SecureDrop 2.1.0-rc1

[zenmonkeykstop]

Status

Ready for review

Description of Changes

Towards #6103 .

Includes changelog updates for 2.1.0 release

Testing

• CI is passing
• staging-test-with-rebase job does run
• changelog additions make sense and capture the required changes in the release

[conorsch]

staging-test-with-rebase job does run

Hmm, that's not happening here. The related PRs are #6063 & #6086. Even after reading the CircleCI docs, the config looks correct to me. But the rebase job definitely hasn't run: https://app.circleci.com/pipelines/github/freedomofpress/securedrop/3028/workflows/8b890766-9b0d-470b-a03a-73aac999b78e

[conorsch]

I appended a small change in an attempt to wake up CI, but no dice. However, I see that the rebase job did run on this branch last night, when it was created:

It's not displayed on the checks for this PR, and indeed it's not running on subsequent commits to this branch in PR state. Presumably that's because the current branch for this PR is update-2.1.0-rc1-changelog, which does not match ^release/.*, and therefore we should only expect it to run the staging job post-merge.

I'll drop the temporary commit and proceed with review, then follow-up post-merge with confirmation that the staging job ran.

[conorsch]

Looks great, thanks for the detail, @zenmonkeykstop. After merge, I'll follow up with debs, as well as check on the staging job in CI, as mentioned above.