feat: auto add a changeset for package updates triggered by bots

[TheOrangePuff]

Description of the proposed changes

• Automatically create a changeset file for PRs opened by Aikido and Dependabot
• This should make the automated PRs more useful. And it means updates will automatically trigger!
• This was mostly vibe coded but heavily watched 👀 What it's doing makes sense to me but it needed a lot of guidance to get there

Example run on this PR #1620:

DRY_RUN=1 .github/scripts/create-bot-changeset.sh origin/main 1620 '[Aikido] Fix 4 security issues in minimatch, ajv'
Updated dependencies:
ajv
minimatch

Affected packages:
@aligent/cdk-aspects
@aligent/cdk-basic-auth
@aligent/cdk-cloudfront-security-headers
@aligent/cdk-domain-hosting
@aligent/cdk-esbuild
@aligent/cdk-geoip-redirect
@aligent/cdk-graphql-mesh-server
@aligent/cdk-header-change-detection
@aligent/cdk-prerender-proxy
@aligent/cdk-rabbitmq
@aligent/cdk-shared-vpc
@aligent/cdk-static-hosting
@aligent/cdk-step-function-from-file
@aligent/cdk-waf

DRY RUN — would create .changeset/bot-pr-1620.md:
---
"@aligent/cdk-aspects": patch
"@aligent/cdk-basic-auth": patch
"@aligent/cdk-cloudfront-security-headers": patch
"@aligent/cdk-domain-hosting": patch
"@aligent/cdk-esbuild": patch
"@aligent/cdk-geoip-redirect": patch
"@aligent/cdk-graphql-mesh-server": patch
"@aligent/cdk-header-change-detection": patch
"@aligent/cdk-prerender-proxy": patch
"@aligent/cdk-rabbitmq": patch
"@aligent/cdk-shared-vpc": patch
"@aligent/cdk-static-hosting": patch
"@aligent/cdk-step-function-from-file": patch
"@aligent/cdk-waf": patch
---

[Aikido] Fix 4 security issues in minimatch, ajv

Notes to reviewers

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