Docusaurus-ify (#26051)

This PR cleans up the docs in a way to make them simpler to ingest by
our [docs repo](https://gitea.com/gitea/gitea-docusaurus).

1. It includes all of the sed invocations our ingestion did, removing
the need to do it at build time.
2. It replaces the shortcode variable replacement method with
`@variable@` style, simply for easier sed invocations when required.
3. It removes unused files and moves the docs up a level as cleanup.

---------

Signed-off-by: jolheiser <john.olheiser@gmail.com>

docs/content/usage/packages/container.en-us.md

@@ -0,0 +1,90 @@
+---
+date: "2021-07-20T00:00:00+00:00"
+title: "Container Registry"
+slug: "container"
+sidebar_position: 30
+draft: false
+toc: false
+menu:
+  sidebar:
+    parent: "packages"
+    name: "Container Registry"
+    sidebar_position: 30
+    identifier: "container"
+---
+
+# Container Registry
+
+Publish [Open Container Initiative](https://opencontainers.org/) compliant images for your user or organization.
+The container registry follows the OCI specs and supports all compatible images like [Docker](https://www.docker.com/) and [Helm Charts](https://helm.sh/).
+
+## Requirements
+
+To work with the Container registry, you can use the tools for your specific image type.
+The following examples use the `docker` client.
+
+## Login to the container registry
+
+To push an image or if the image is in a private registry, you have to authenticate:
+
+```shell
+docker login gitea.example.com
+```
+
+If you are using 2FA or OAuth use a [personal access token](development/api-usage.md#authentication) instead of the password.
+
+## Image naming convention
+
+Images must follow this naming convention:
+
+`{registry}/{owner}/{image}`
+
+For example, these are all valid image names for the owner `testuser`:
+
+`gitea.example.com/testuser/myimage`
+
+`gitea.example.com/testuser/my-image`
+
+`gitea.example.com/testuser/my/image`
+
+**NOTE:** The registry only supports case-insensitive tag names. So `image:tag` and `image:Tag` get treated as the same image and tag.
+
+## Push an image
+
+Push an image by executing the following command:
+
+```shell
+docker push gitea.example.com/{owner}/{image}:{tag}
+```
+
+| Parameter | Description |
+| ----------| ----------- |
+| `owner`   | The owner of the image. |
+| `image`   | The name of the image. |
+| `tag`     | The tag of the image. |
+
+For example:
+
+```shell
+docker push gitea.example.com/testuser/myimage:latest
+```
+
+## Pull an image
+
+Pull an image by executing the following command:
+
+```shell
+docker pull gitea.example.com/{owner}/{image}:{tag}
+```
+
+| Parameter | Description |
+| ----------| ----------- |
+| `owner`   | The owner of the image. |
+| `image`   | The name of the image. |
+| `tag`     | The tag of the image. |
+
+For example:
+
+```shell
+docker pull gitea.example.com/testuser/myimage:latest
+```