Editorial: Fix formatting of grammar productions ending in html entiies

A bug in grammarkdown (which is fixed in master and not yet released)
causes a newline after an html entity to get consumed, making
alternatives run together and look like a seqence of symbols.

This commit works around the bug by adding a trailing space after html
entities in grammar productions.

See rbuckton/grammarkdown#29 for the proper fix
which has yet to be released.

spec.html

@@ -9575,13 +9575,13 @@ <h1>White Space</h1>
     <h2>Syntax</h2>
     <emu-grammar type="definition">
       WhiteSpace ::
-        &lt;TAB&gt;
-        &lt;VT&gt;
-        &lt;FF&gt;
-        &lt;SP&gt;
-        &lt;NBSP&gt;
-        &lt;ZWNBSP&gt;
-        &lt;USP&gt;
+        &lt;TAB&gt; 
+        &lt;VT&gt; 
+        &lt;FF&gt; 
+        &lt;SP&gt; 
+        &lt;NBSP&gt; 
+        &lt;ZWNBSP&gt; 
+        &lt;USP&gt; 
     </emu-grammar>
   </emu-clause>
 
@@ -9656,17 +9656,17 @@ <h1>Line Terminators</h1>
     <h2>Syntax</h2>
     <emu-grammar type="definition">
       LineTerminator ::
-        &lt;LF&gt;
-        &lt;CR&gt;
-        &lt;LS&gt;
-        &lt;PS&gt;
+        &lt;LF&gt; 
+        &lt;CR&gt; 
+        &lt;LS&gt; 
+        &lt;PS&gt; 
 
       LineTerminatorSequence ::
-        &lt;LF&gt;
+        &lt;LF&gt; 
         &lt;CR&gt; [lookahead != &lt;LF&gt; ]
-        &lt;LS&gt;
-        &lt;PS&gt;
-        &lt;CR&gt; &lt;LF&gt;
+        &lt;LS&gt; 
+        &lt;PS&gt; 
+        &lt;CR&gt; &lt;LF&gt; 
     </emu-grammar>
   </emu-clause>
 
@@ -9749,14 +9749,14 @@ <h2>Syntax</h2>
         UnicodeIDContinue
         `$`
         `\` UnicodeEscapeSequence
-        &lt;ZWNJ&gt;
-        &lt;ZWJ&gt;
+        &lt;ZWNJ&gt; 
+        &lt;ZWJ&gt; 
 
       UnicodeIDStart ::
-        &gt; any Unicode code point with the Unicode property &ldquo;ID_Start&rdquo;
+        &gt; any Unicode code point with the Unicode property &ldquo;ID_Start&rdquo; 
 
       UnicodeIDContinue ::
-        &gt; any Unicode code point with the Unicode property &ldquo;ID_Continue&rdquo;
+        &gt; any Unicode code point with the Unicode property &ldquo;ID_Continue&rdquo; 
     </emu-grammar>
     <p>The definitions of the nonterminal |UnicodeEscapeSequence| is given in <emu-xref href="#sec-literals-string-literals"></emu-xref>.</p>
     <emu-note>
@@ -10199,15 +10199,15 @@ <h2>Syntax</h2>
 
         DoubleStringCharacter ::
           SourceCharacter but not one of `"` or `\` or LineTerminator
-          &lt;LS&gt;
-          &lt;PS&gt;
+          &lt;LS&gt; 
+          &lt;PS&gt; 
           `\` EscapeSequence
           LineContinuation
 
         SingleStringCharacter ::
           SourceCharacter but not one of `'` or `\` or LineTerminator
-          &lt;LS&gt;
-          &lt;PS&gt;
+          &lt;LS&gt; 
+          &lt;PS&gt; 
           `\` EscapeSequence
           LineContinuation
 
@@ -28941,8 +28941,8 @@ <h2>Syntax</h2>
           UnicodeIDContinue
           `$`
           `\` RegExpUnicodeEscapeSequence[?U]
-          &lt;ZWNJ&gt;
-          &lt;ZWJ&gt;
+          &lt;ZWNJ&gt; 
+          &lt;ZWJ&gt; 
 
         RegExpUnicodeEscapeSequence[U] ::
           [+U] `u` LeadSurrogate `\u` TrailSurrogate