docs: restore section template comments in ndarray/base/diagonal and ndarray/last

PR-URL: #11903
Reviewed-by: Athan Reines <kgryte@gmail.com>

Author: Planeshifter

lib/node_modules/@stdlib/ndarray/base/diagonal/README.md

@@ -22,6 +22,8 @@ limitations under the License.
 
 > Return a view of the diagonal of a matrix (or stack of matrices).
 
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
 <section class="intro">
 
 For an `M`-by-`N` matrix `A`, the `k`-th diagonal is defined as
@@ -60,6 +62,8 @@ the main diagonal is `[ a_{0,0}, a_{1,1}, a_{2,2} ]`, the super-diagonal `k = 1`
 
 <!-- /.intro -->
 
+<!-- Package usage documentation. -->
+
 <section class="usage">
 
 ## Usage
@@ -93,6 +97,8 @@ The function accepts the following arguments:
 
 <!-- /.usage -->
 
+<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
 <section class="notes">
 
 ## Notes
@@ -107,6 +113,8 @@ The function accepts the following arguments:
 
 <!-- /.notes -->
 
+<!-- Package usage examples. -->
+
 <section class="examples">
 
 ## Examples
@@ -141,6 +149,8 @@ console.log( ndarray2array( y ) );
 
 <!-- /.examples -->
 
+<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
 <section class="references">
 
 </section>

lib/node_modules/@stdlib/ndarray/last/README.md

@@ -22,7 +22,7 @@ limitations under the License.
 
 > Return a read-only view of the last element (or subarray) along one or more [`ndarray`][@stdlib/ndarray/ctor] dimensions.
 
-<!-- Section to include introductory text. Make sure to keep an empty line after the intro section element. -->
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
 
 <section class="intro">