Add documentation for PackageDependencies (#510)

* Add documentation for PackageDependencies and update relevant docs with links to it

* Update dependenceies with better descriptions and info

website/docs/dependencies.md

@@ -0,0 +1,97 @@
+---
+title: Dependencies
+---
+
+`PackageDependencies` specifies dependency information for a particular package.  This includes dependencies for runtime, which will be installed along with the package by the package manager, as well as any dependencies needed to build and/or test the resulting package. Configuration for any additional package repositories which are required may also be added here.
+
+### Fields
+
+- **Build**: The list of packages required to build the package.
+    ```yaml
+    build:
+      package_name:
+          version: [">=1.0.0", "<2.0.0"]
+          arch: ["amd64", "arm64"]
+    ```
+
+- **Runtime**: The list of packages required to install/run the package.
+    ```yaml
+    runtime:
+      package_name:
+          version: [">=1.0.0", "<2.0.0"]
+          arch: ["amd64", "arm64"]
+    ```
+
+- **Recommends**: The list of packages recommended to install with the generated package.
+    ```yaml
+    recommends:
+      package_name:
+          version: [">=1.0.0", "<2.0.0"]
+          arch: ["amd64", "arm64"]
+    ```
+
+:::note
+Each of the above fields is a list of [PackageConstraints](https://pkg.go.dev/github.com/Azure/dalec#PackageConstraints).
+:::
+
+- **Test**: Lists and extra packages required for running tests. These are only installed for tests which have steps that require running a command in the built container. See [TestSpec](https://pkg.go.dev/github.com/Azure/dalec#TestSpec) for more information
+    ```yaml
+    test:
+      - package_name_1
+      - package_name_2
+    ```
+
+- **ExtraRepos**: Used to inject extra package repositories that may be used to satisfy package dependencies in various stages. 
+    ```yaml
+    extra_repos:
+      - keys:
+          mykey:
+            http:
+              URL: "https://example.com/mykey.gpg"
+              permissions: 0644
+        config: 
+          myrepo:
+            http:
+              url: "https://example.com/myrepo.list"
+        data: 
+          - dest: "/path/to/dest"
+            spec: source
+        envs: ["build", "test", "install"] 
+    ```
+    See [repositories](repositories.md) for more details on repository configs.
+
+### Example
+```yaml
+dependencies:
+  build:
+    gcc:
+      version: [">=9.0.0"]
+      arch: ["amd64"]
+  runtime:
+    libc6:
+      version: [">=2.29"]
+  recommends:
+    curl:
+      version: [">=7.68.0"]
+  test:
+    - bats
+  extra_repos:
+    - keys:
+        mykey: 
+          http:
+            url: "https://example.com/mykey.gpg"
+            permissions: 0644
+      config:
+        myrepo:
+          http:
+            url: "https://example.com/myrepo.list"
+      # this assumes that a build context named `my-local-repo` containing a local repository will be passed 
+      # to the Dalec build.
+      # /opt/repo can now be referenced as a local repository in a repository config imported to dalec
+      data:
+        - dest: "/opt/repo"
+          spec:
+            context:
+              name: "my-local-repo"
+      envs: ["build", "install"]
+```

website/docs/spec.md

@@ -171,8 +171,24 @@ dependencies:
   runtime:
     - libfoo
     - libbar
+  recommends:
+    - libcafe
+  test:
+    - kind
+  extra_repos:
+    - libdecaf
 ```
 
+`Build` dependencies are the list of packages required to build the package.
+
+`Runtime` dependencies are the list of packages required to install/run the package.
+
+`Recommends` dependencies are the list of packages recommended to install with the generated package.
+
+`Test` dependencies list packages required for running tests. These packages are only installed for tests which have steps that require running a command in the built container.
+
+See [dependencies](dependencies.md) for more details on dependency options.
+
 Sometimes you may need to add extra repositories in order to fulfill the
 specified dependencies.
 You can do this by adding these to the `extra_repos` field.

website/sidebars.ts

@@ -29,6 +29,7 @@ const sidebars: SidebarsConfig = {
       items: [
         'spec',
         'sources',
+        'dependencies',
         'targets',
         'testing',
         'artifacts',