Explain on the agreement that legal name is required

See whatwg/html#10780 (comment).

views/agreement.hbs

@@ -58,11 +58,12 @@ input[readonly] {
  grid-template-columns: auto 1fr;
  grid-column-gap: 20px;
  grid-row-gap: 1em;
- justify-items: stretch; /* Edge does not stretch inputs inside grids by default */
 }
 
-.grid-form label {
- display: block; /* this gives a fallback that displays reasonably in non-grid browsers */
+.explanation {
+ grid-column: 2;
+ margin-top: -1em;
+ color: #333;
 }
 
 .signature-section-container {
@@ -202,6 +203,7 @@ input[type="submit"] {
    <div class="grid-form signature-section-container">
     <label for="individual-name">Name:</label>
     <input type="text" name="individual-name" id="individual-name" required>
+    <small class="explanation">This must be your legal name, that you use in the real world to sign contracts. It <a href="https://github.com/whatwg/sg/issues/93#issuecomment-1120799691">cannot be a pseudonym</a>.</small>
 
     <label for="individual-address">City + Country:</label>
     <input type="text" name="individual-address" id="individual-address" required>