chore(seed): add tags and links to changelog entries

[armandobelardo]

Fixes FER-3266

Note that this doesn't add in any automation to add the PR link since it seemed a bit complex for the up side

Down the line I can see us adding a changelog bot, as we've seen in the past, which automates this away (and will make grabbing the PR link much easier)

This PR introduces a new feature to the Fern CLI and Seed packages, allowing users to specify allowed tags for changelog validation.

Changes

• The allowedTags property is added to the CliSeedWorkspaceConfiguration and SeedWorkspaceConfiguration interfaces in the config.yml file.
• The validateCliChangelog and validateGeneratorChangelog functions are updated to include the allowedTags parameter.
• The allowedTags property is added to the cliWorkspace.workspaceConfig and generatorConfig objects.
• The allowedTags property is added to the package.json files in the cli and core packages.
• The allowedTags property is added to the versions.yml file in the cli package.
• The allowedTags property is added to the seed.yml file in the seed package.