build: switch to docs-content from examples package (#14612)

With https://github.com/angular/material.angular.io/pull/565 the docs-content will be pulled from the `@angular/material-examples` package. Changes needed on this repository:

* Since we update some styles and logic in favor of simplicity, we need to update the Dgeni templates to conform with these changes.
* Remove the unnecessary `examplesPath` property member because we now compute the `docs-content/` asset paths in a consistent way and don't want to mix up the source locations.

tools/dgeni/templates/constant.template.html

@@ -15,6 +15,7 @@
   <p class="docs-api-constant-description">{$ constant.description | marked | safe $}</p>
 {%- endif -%}
 
+<div class="docs-markdown">
 <pre class="docs-markdown-pre">
 <code class="docs-markdown-code">
 {%- highlight "typescript" -%}
@@ -22,3 +23,4 @@
 {%- end_highlight -%}
 </code>
 </pre>
+</div>

tools/dgeni/templates/type-alias.template.html

@@ -15,6 +15,7 @@
   <p class="docs-api-type-alias-description">{$ alias.description | marked | safe $}</p>
 {%- endif -%}
 
+<div class="docs-markdown">
 <pre class="docs-markdown-pre">
 <code class="docs-markdown-code">
 {%- highlight "typescript" -%}
@@ -22,3 +23,4 @@
 {%- end_highlight -%}
 </code>
 </pre>
+</div>

tools/package-docs-content/package-docs-content.ts

@@ -26,8 +26,8 @@ function getBazelActionArguments() {
 }
 
 if (require.main === module) {
-  // The script expects the output path as first argument. All remaining arguments will be
-  // considered as markdown input files that need to be transformed.
+  // Process all file pairs that have been passed to this executable. Each argument will
+  // consist of the input file path and the desired output location.
   getBazelActionArguments().forEach(argument => {
     // Each argument that has been passed consists of an input file path and the expected
     // output path. e.g. {path_to_input_file},{expected_output_path}