build(aio): move doc-gen stuff from angular.io (#14097)

docs/templates/lib/githubLinks.html

@@ -0,0 +1,7 @@
+{% macro githubHref(doc, versionInfo) -%}
+https://github.com/{$ versionInfo.gitRepoInfo.owner $}/{$ versionInfo.gitRepoInfo.repo $}/tree/{$ versionInfo.currentVersion.isSnapshot and versionInfo.currentVersion.SHA or versionInfo.currentVersion.raw $}/modules/{$ doc.fileInfo.projectRelativePath $}#L{$ doc.location.start.line+1 $}-L{$ doc.location.end.line+1 $}
+{%- endmacro %}
+
+{% macro githubViewLink(doc, versionInfo) -%}
+  <a href="{$ githubHref(doc, versionInfo) $}">{$ doc.fileInfo.projectRelativePath $}</a>
+{%- endmacro %}

docs/templates/lib/paramList.html

@@ -0,0 +1,12 @@
+{% macro paramList(params) -%}
+  {%- if params -%}
+    ({%- for param in params -%}
+      {$ param | escape $}{% if not loop.last %}, {% endif %}
+    {%- endfor %})
+  {%- endif %}
+{%- endmacro -%}
+
+
+{% macro returnType(returnType) -%}
+  {%- if returnType %} : {$ returnType | escape $}{% endif -%}
+{%- endmacro -%}