feat: make forge configurable in GitHub Action

Forgejo actions are a near drop-in replacement for GitHub actions. This
commit changes the action.yml file to make the forge configurable. This
allows using the action with forgejo instances.

Changes made:

- Introduce a `forge` input and pass it as the value of the `--forge`
  flag.
- Introduce `api-url` input and pass it as the value of the `--api-url`
  flag. This is required to configure the API URL of the forge. If the
  action is used with GitHub Actions it is simply ignored.
- Pass `inputs.token` as value to the `--api-token` flag. This is
  required as the forgejo client does not respect the `GITHUB_ACTION`
  environment variable.
- Introduce `owner` input and pass it as the value of the `--owner`
  flag. As this was not passed before the default is set to `""`. In
  theory it could be set to the value of `github.repository_owner`.
- Introduce `user` input and pass it as the value of the `--user`
  flag. As this was not passed before the default is set to `""`. GitHub
  Actions does not seem to provide a convenient way to get the
  repository without the owner. As such keeping it at `""` for the
  default is safest.

action.yml

@@ -21,6 +21,22 @@ inputs:
     description: "List of updaters that are run. Default updaters can be removed by specifying them as -name. Multiple updaters should be concatenated with a comma. Default Updaters: changelog,generic"
     required: false
     default: ""
+  forge:
+    description: "Forge this action is run against"
+    required: false
+    default: "github"
+  api-url:
+    description: "API URL of the selected forge "
+    required: false
+    default: ""
+  owner:
+    description: "Owner of the repository"
+    required: false
+    default: ""
+  repo:
+    description: "Name of the repository"
+    required: false
+    default: ""
   # Remember to update docs/reference/github-action.md
 outputs: { }
 runs:
@@ -28,10 +44,14 @@ runs:
   image: docker://ghcr.io/apricote/releaser-pleaser:v0.7.1 # x-releaser-pleaser-version
   args:
     - run
-    - --forge=github
+    - --forge=${{ inputs.forge }}
     - --branch=${{ inputs.branch }}
     - --extra-files="${{ inputs.extra-files }}"
     - --updaters="${{ inputs.updaters }}"
+    - --api-url=${{ inputs.api-url }}
+    - --api-token=${{ inputs.token }}
+    - --owner=${{ inputs.owner }}
+    - --repo=${{ inputs.repo }}
   env:
     GITHUB_TOKEN: "${{ inputs.token }}"
     GITHUB_USER: "oauth2"