Add related articles to Memory and Span types (#3803)

* Add related articles to Memory and Span types

* Add articles to ReadOnly types as well

* suggestions by mairaw

Co-Authored-By: Maira Wenzel <[email protected]>

Co-authored-by: Maira Wenzel <[email protected]>

Author: carlossanlop

xml/System/Memory`1.xml

@@ -51,6 +51,8 @@ In addition to `Memory<T>`, you can use <xref:System.ReadOnlyMemory%601?displayP
 
     ]]></format>
     </remarks>
+    <related type="article" href="~/docs/standard/memory-and-spans/index.md">Memory- and span-related types</related>
+    <related type="article" href="~/docs/standard/memory-and-spans/memory-t-usage-guidelines.md">Memory&lt;T&gt; and Span&lt;T&gt; usage guidelines</related>
   </Docs>
   <Members>
     <Member MemberName=".ctor">

xml/System/ReadOnlyMemory`1.xml

@@ -37,6 +37,8 @@
     <typeparam name="T">The object type from which the contiguous region of memory will be read.</typeparam>
     <summary>Represents a contiguous region of memory, similar to <see cref="T:System.ReadOnlySpan`1" />. Unlike <see cref="T:System.ReadOnlySpan`1" />, it is not a byref-like type.</summary>
     <remarks>To be added.</remarks>
+    <related type="article" href="~/docs/standard/memory-and-spans/index.md">Memory- and span-related types</related>
+    <related type="article" href="~/docs/standard/memory-and-spans/memory-t-usage-guidelines.md">Memory&lt;T&gt; and Span&lt;T&gt; usage guidelines</related>
   </Docs>
   <Members>
     <Member MemberName=".ctor">

xml/System/ReadOnlySpan`1.xml

@@ -41,6 +41,8 @@
 
 A `ReadOnlySpan<T>` instance is often used to reference the elements of an array or a portion of an array. Unlike an array, however, a `ReadOnlySpan<T>` instance can point to managed memory, native memory, or memory managed on the stack.]]></format>
     </remarks>
+    <related type="article" href="~/docs/standard/memory-and-spans/index.md">Memory- and span-related types</related>
+    <related type="article" href="~/docs/standard/memory-and-spans/memory-t-usage-guidelines.md">Memory&lt;T&gt; and Span&lt;T&gt; usage guidelines</related>
   </Docs>
   <Members>
     <Member MemberName=".ctor">

xml/System/Span`1.xml

@@ -87,6 +87,8 @@ This allocation and copy operation can be eliminated by using either `Span<T>` o
 
       ]]></format>
     </remarks>
+    <related type="article" href="~/docs/standard/memory-and-spans/index.md">Memory- and span-related types</related>
+    <related type="article" href="~/docs/standard/memory-and-spans/memory-t-usage-guidelines.md">Memory&lt;T&gt; and Span&lt;T&gt; usage guidelines</related>
   </Docs>
   <Members>
     <Member MemberName=".ctor">