uSync.Migrations: repo standards, CI overhaul, and v17.0.1 release

Repo: Jumoo/uSyncMigrations

Added repo standards (README, CHANGELOG, SECURITY, CODE_OF_CONDUCT, .editorconfig, global.json, locked NuGet restores) and CI workflows (PR build, package build, CodeQL, release) matching the Xliff.Connector standard
Switched the release workflow from a stored NuGet API key to GitVersion + NuGet trusted publishing (OIDC)
Fixed a YAML folding bug in the new build/pack workflow loops that broke dotnet build/dotnet pack with a bogus -c: command not found
Merged #321: loosened the macro migration guard so JSON-encoded macros (<?UMBRACO_MACRO) actually get converted
Released v17.0.1 to NuGet — first release since 17.0.0