Update operator precedence table (#2625)

* Update operator precedence table

Updates the table to match the information per the parser.

This adds entries for:
* `=>`
* `include`, `include_once`, `require`, `require_once`
* `fn`
* `throw`

Ref: https://github.com/php/php-src/blob/2e2416825d2270d256f7597904e14e386cc0d854/Zend/zend_language_parser.y#L54-L82

Fixes 2622

* Operator precedence table: change links for double arrow to yield

* Operator precedence table: attempt to clarify fn arrow entry

* Operator precedence table: attempt to clarify fn arrow entry [2]

---------

Co-authored-by: jrfnl <jrfnl@users.noreply.github.com>

Author: jrfnl

language/operators/precedence.xml

@@ -256,6 +256,13 @@
        <link linkend="control-structures.yield.from">yield from</link>
       </entry>
      </row>
+     <row>
+      <entry>(n/a)</entry>
+      <entry><literal>=&gt;</literal></entry>
+      <entry>
+       <link linkend="language.generators.syntax">yield with keys</link>
+      </entry>
+     </row>
      <row>
       <entry>(n/a)</entry>
       <entry><literal>yield</literal></entry>
@@ -289,6 +296,26 @@
        <link linkend="language.operators.logical">logical</link>
       </entry>
      </row>
+     <row>
+      <entry>(n/a)</entry>
+      <entry>
+       <literal>include</literal>
+       <literal>include_once</literal>
+       <literal>require</literal>
+       <literal>require_once</literal>
+      </entry>
+      <entry>
+       <function>include</function>,
+       <function>include_once</function>,
+       <function>require</function>&listendand;
+       <function>require_once</function>
+      </entry>
+     </row>
+     <row>
+      <entry>(n/a)</entry>
+      <entry><literal>fn (...) =&gt;</literal></entry>
+      <entry><link linkend="functions.arrow">fn arrow</link> disambiguity</entry>
+     </row>
      <row>
       <entry>(n/a)</entry>
       <entry><literal>throw</literal></entry>