(SCHEMA) Fix extension schemas

Prior to this change, the extension schemas were
erroneously placed in the `extensions` folder
instead of the `extension` folder. The schema
for the output from `dsc extension list` was
missing as was the schema for extension
capabilities.

This change renames the folder and adds the
missing schemas.

Author: michaeltlombardi

schemas/src/definitions/extensionCapabilities.yaml

@@ -0,0 +1,40 @@
+# yaml-language-server: $schema=https://json-schema.org/draft/2020-12/schema
+$schema: https://json-schema.org/draft/2020-12/schema
+$id:     <HOST>/<PREFIX>/<VERSION>/definitions/extensionCapabilities.yaml
+
+title: Resource capabilities
+description: >-
+  Define the operations DSC can invoke for an extension and how the extension behaves when invoked.
+  
+markdownDescription: |-
+  ***
+  [_Online Documentation_][00]
+  ***
+
+  DSC extensions always have at least one capability. Extension capabilities define the operations
+  DSC can invoke for an extension and how the extension behaves when invoked.
+
+  <!-- Link reference definitions -->
+  [00]: <DOCS_BASE_URL>/reference/schemas/definitions/extensionCapabilities?<DOCS_VERSION_PIN>
+
+type: array
+items:
+  type: string
+  enum:
+    - discover
+  markdownEnumDescriptions:
+    - |- # discover
+      ***
+      [_Online Documentation_][00]
+      ***
+
+      An extension with the `discover` capability supports retrieving the path to DSC resource
+      manifests that aren't included in the `PATH` or `DSC_RESOURCE_PATH`, like manifests for
+      software installed as AppX packages.
+
+      An extension has this capability when its manifest defines the [discover][02]
+      property.
+
+      <!-- Link reference definitions -->
+      [00]: <DOCS_BASE_URL>/reference/schemas/definitions/extensionCapabilities?<DOCS_VERSION_PIN>#discover
+      [02]: <DOCS_BASE_URL>/reference/schemas/extension/manifest/discover?<DOCS_VERSION_PIN>

schemas/src/extensions/manifest.discover.yaml renamed to schemas/src/extension/manifest.discover.yaml

@@ -0,0 +1,44 @@
+# yaml-language-server: $schema=https://json-schema.org/draft/2020-12/schema
+$schema: https://json-schema.org/draft/2020-12/schema
+$id:     <HOST>/<PREFIX>/<VERSION>/outputs/extension/list.yaml
+
+title: dsc extension list result
+description: >-
+  Describes the return data for a DSC extension instance from the
+  `dsc extension list` command.
+
+type: object
+properties:
+  type:
+    $ref: /<PREFIX>/<VERSION>/definitions/extensionType.yaml
+  version:
+    $ref: /<PREFIX>/<VERSION>/definitions/semver.yaml
+  capabilities:
+    $ref: /<PREFIX>/<VERSION>/definitions/extensionCapabilities.yaml
+  description:
+    title: Extension description
+    description: >-
+      A short synopsis of the DSC extension's purpose.
+    # Should this include a maximum length or a pattern that forbids newlines?
+    type: string
+  path:
+    title: Path
+    description: >-
+      Indicates the path to the DSC extension on the file system.
+    type: string
+  directory:
+    title: Directory
+    description: >-
+      Indicates the path to the folder containing the DSC extension on the file
+      system.
+    type: string
+  author:
+    title: Author
+    description: >-
+      Indicates the name of the person or organization that developed and
+      maintains the DSC extension.
+    type:
+      - string
+      - 'null'
+  manifest:
+    $ref: /<PREFIX>/<VERSION>/extension/manifest.yaml