Add documentation on how to create a sublanding page (github#17467)

Co-authored-by: Emily Gould <4822039+emilyistoofunky@users.noreply.github.com>
Co-authored-by: Cynthia Rich <crichID@users.noreply.github.com>

content/README.md

@@ -21,6 +21,10 @@ See the [contributing docs](/CONTRIBUTING.md) for general information about work
   - [`miniTocMaxHeadingLevel`](#minitocmaxheadinglevel)
   - [`allowTitleToDifferFromFilename`](#allowtitletodifferfromfilename)
   - [`defaultPlatform`](#defaultplatform)
+  - [`learningTracks`](#learningTracks)
+  - [`includeGuides`](#includeGuides)
+  - [`type`](#type)
+  - [`topics`](#topics)
   - [Escaping single quotes](#escaping-single-quotes)
 - [Autogenerated mini TOCs](#autogenerated-mini-tocs)
 - [Versioning](#versioning)
@@ -29,6 +33,7 @@ See the [contributing docs](/CONTRIBUTING.md) for general information about work
 - [Whitespace control](#whitespace-control)
 - [Links and image paths](#links-and-image-paths)
   - [Preventing transformations](#preventing-transformations)
+- [Creating new sublanding pages](#creating-new-sublanding-pages)
 
 ## Frontmatter
 
@@ -186,6 +191,39 @@ Example:
 defaultPlatform: linux
 ```
 
+### `learningTracks`
+- Purpose: Render a list of learning tracks on a product's sub-landing page.
+- type: `String`. This should reference learning tracks' names defined in [`data/learning-tracks/*.yml`](../data/learning-tracks/README.md).
+- Optional
+
+**Note: the first learning track is by-default the featured track.*
+
+### `includeGuides`
+- Purpose: Render a list of articles, filterable by `type` and `topics`. Only applicable when used with `layout: product-sublanding`.
+- Type: `Array`
+- Optional.
+
+Example:
+
+```yml
+includeGuides:
+  - /actions/guides/about-continuous-integration
+  - /actions/guides/setting-up-continuous-integration-using-workflow-templates
+  - /actions/guides/building-and-testing-nodejs
+  - /actions/guides/building-and-testing-powershell
+```
+
+### `type`
+- Purpose: Indicate the type of article. 
+- Type: `String`, one of the `overview`, `quick_start`, `tutorial`, `how_to`, `reference`.
+- Optional.
+
+### `topics`
+- Purpose: Indicate the topics covered by the article.
+- Type: `String`
+- Optional.
+
+
 ### Escaping single quotes
 
 If you see two single quotes in a row (`''`) in YML frontmatter where you might expect to see one (`'`), this is the YML-preferred way to escape a single quote. From [the YAML spec](https://yaml.org/spec/history/2001-12-10.html):
@@ -274,3 +312,15 @@ Sometimes you want to link to a Dotcom-only article in Enterprise content and yo
 ```
 
 Sometimes the canonical home of content moves outside the docs site. None of the links included in [`lib/redirects/external-sites.json`](/lib/redirects/external-sites.json) get rewritten. See  [`contributing/redirects.md`](/contributing/redirects.md) for more info about this type of redirect.
+
+
+### Creating new sublanding pages
+
+To create a sublanding page (e.g. [Actions' Guide page](https://docs.github.com/en/actions/guides)), create or modify an existing markdown file with these specific frontmatter values:
+
+1. Use the sublanding page template by referencing it `layout: product-sublanding`
+2. (optional) Include the learning tracks in [`learningTracks`](#learningTracks)
+3. (optional) Define which articles to include with [`includeGuides`](#includeGuides).
+
+If using learning tracks, they need to be defined in [`data/learning-tracks/*.yml`](../data/learning-tracks/README.md).
+If using `includeGuides`, make sure each of the articles in this list has [`topics`](#topics) and [`type`](#type) in its frontmatter.

data/README.md

@@ -27,3 +27,7 @@ Webhook payload JSON files are used in the [`webhook events docs`](../content/de
 ## ui.yml
 
 `ui.yml` contains localized strings used in HTML layouts.
+
+## Learning Tracks
+
+Learning tracks are a collection of articles that help you master a particular subject. See [learning-tracks/README.md](learning-tracks/README.md).

data/learning-tracks/README.md

@@ -0,0 +1,3 @@
+# Learning Tracks (aka Learning Paths)
+
+Learning tracks are a collection of articles that help you master a particular subject. Learning tracks are defined on a per-product basis.