feat(provider): add repository label resource

Closes #16

docs/resources/repository_label.md

@@ -0,0 +1,44 @@
+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "forgejo_repository_label Resource - terraform-provider-forgejo"
+subcategory: ""
+description: |-
+  Use this resource to create and manage a repository label.
+---
+
+# forgejo_repository_label (Resource)
+
+Use this resource to create and manage a repository label.
+
+## Example Usage
+
+```terraform
+resource "forgejo_repository_label" "main" {
+  color       = "0000ff"
+  description = "blue label"
+  name        = "test"
+  owner       = "adyxax"
+  repository  = "example"
+}
+```
+
+<!-- schema generated by tfplugindocs -->
+## Schema
+
+### Required
+
+- `color` (String) The label's color in lowercase rgb format, without a leading `#`. For example `207de5`.
+- `description` (String) A description string.
+- `name` (String) The label's name.
+- `owner` (String) The variable's owner.
+- `repository` (String) The label's repository.
+
+### Optional
+
+- `exclusive` (Boolean) Whether the label is exclusive or not. Defaults to `false`. Name the label `scope/item` to make it mutually exclusive with other `scope/` labels.
+- `is_archived` (Boolean) Whether the repository label is archived or not. Defaults to `false`
+
+### Read-Only
+
+- `id` (Number) The identifier of the repository label.
+- `url` (String) The repository label's URL.