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/rubygems.en-us.md

@@ -0,0 +1,124 @@
+---
+date: "2021-07-20T00:00:00+00:00"
+title: "RubyGems Package Registry"
+slug: "rubygems"
+sidebar_position: 110
+draft: false
+toc: false
+menu:
+  sidebar:
+    parent: "packages"
+    name: "RubyGems"
+    sidebar_position: 110
+    identifier: "rubygems"
+---
+
+# RubyGems Package Registry
+
+Publish [RubyGems](https://guides.rubygems.org/) packages for your user or organization.
+
+## Requirements
+
+To work with the RubyGems package registry, you need to use the [gem](https://guides.rubygems.org/command-reference/) command line tool to consume and publish packages.
+
+## Configuring the package registry
+
+To register the package registry edit the `~/.gem/credentials` file and add:
+
+```ini
+---
+https://gitea.example.com/api/packages/{owner}/rubygems: Bearer {token}
+```
+
+| Parameter     | Description |
+| ------------- | ----------- |
+| `owner`       | The owner of the package. |
+| `token`       | Your [personal access token](development/api-usage.md#authentication). |
+
+For example:
+
+```
+---
+https://gitea.example.com/api/packages/testuser/rubygems: Bearer 3bd626f84b01cd26b873931eace1e430a5773cc4
+```
+
+## Publish a package
+
+Publish a package by running the following command:
+
+```shell
+gem push --host {host} {package_file}
+```
+
+| Parameter      | Description |
+| -------------- | ----------- |
+| `host`         | URL to the package registry. |
+| `package_file` | Path to the package `.gem` file. |
+
+For example:
+
+```shell
+gem push --host https://gitea.example.com/api/packages/testuser/rubygems test_package-1.0.0.gem
+```
+
+You cannot publish a package if a package of the same name and version already exists. You must delete the existing package first.
+
+## Install a package
+
+To install a package from the package registry you can use [Bundler](https://bundler.io) or `gem`.
+
+### Bundler
+
+Add a new `source` block to your `Gemfile`:
+
+```
+source "https://gitea.example.com/api/packages/{owner}/rubygems" do
+  gem "{package_name}"
+end
+```
+
+| Parameter         | Description |
+| ----------------- | ----------- |
+| `owner`           | The owner of the package. |
+| `package_name`    | The package name. |
+
+For example:
+
+```
+source "https://gitea.example.com/api/packages/testuser/rubygems" do
+  gem "test_package"
+end
+```
+
+Afterwards run the following command:
+
+```shell
+bundle install
+```
+
+### gem
+
+Execute the following command:
+
+```shell
+gem install --host https://gitea.example.com/api/packages/{owner}/rubygems {package_name}
+```
+
+| Parameter         | Description |
+| ----------------- | ----------- |
+| `owner`           | The owner of the package. |
+| `package_name`    | The package name. |
+
+For example:
+
+```shell
+gem install --host https://gitea.example.com/api/packages/testuser/rubygems test_package
+```
+
+## Supported commands
+
+```
+gem install
+bundle install
+gem push
+```