feat(provider): add repository push mirror resource

Closes #12

docs/resources/repository_push_mirror.md

@@ -0,0 +1,45 @@
+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "forgejo_repository_push_mirror Resource - terraform-provider-forgejo"
+subcategory: ""
+description: |-
+  Use this resource to create and manage a repository push mirror.
+---
+
+# forgejo_repository_push_mirror (Resource)
+
+Use this resource to create and manage a repository push mirror.
+
+## Example Usage
+
+```terraform
+resource "forgejo_repository_push_mirror" "main" {
+  owner           = "adyxax"
+  remote_address  = "https://github.com/adyxax/tfstated"
+  remote_password = "secret"
+  remote_username = "adyxax"
+  repository      = "example"
+}
+```
+
+<!-- schema generated by tfplugindocs -->
+## Schema
+
+### Required
+
+- `owner` (String) The owner of the repository on which to configure a push mirror.
+- `remote_address` (String) The push mirror's remote address.
+- `repository` (String) The repository on which to configure a push mirror.
+
+### Optional
+
+- `interval` (String) The push mirror's sync interval as a string. Defaults to `8h0m0s`.
+- `remote_password` (String, Sensitive) The push mirror's remote password.
+- `remote_username` (String) The push mirror's remote username.
+- `sync_on_commit` (Boolean) Whether the push mirror is synced on each commit pushed to the repository, defaults to `true`.
+- `use_ssh` (Boolean) Whether the push mirror is synced over SSH or not (not meaning HTTP), defaults to `false`.
+
+### Read-Only
+
+- `created` (String) The push mirror's creation date and time.
+- `name` (String) The name of the push mirror.