Update files for 1.7.15 release

Author: gbrail

README.md

@@ -14,6 +14,7 @@ The current release is <a href="https://github.com/mozilla/rhino/releases/tag/Rh
 
 <details><summary>Releases</summary>
 <table>
+<tr><td><a href="https://github.com/mozilla/rhino/releases/tag/Rhino1_7_15_Release">Rhino 1.7.15</a></td><td>May 3, 2024</td></tr>
 <tr><td><a href="https://github.com/mozilla/rhino/releases/tag/Rhino1_7_14_Release">Rhino 1.7.14</a></td><td>January 6, 2022</td></tr>
 <tr><td><a href="https://github.com/mozilla/rhino/releases/tag/Rhino1_7_13_Release">Rhino 1.7.13</a></td><td>September 2, 2020</td></tr>
 <tr><td><a href="https://github.com/mozilla/rhino/releases/tag/Rhino1_7_12_Release">Rhino 1.7.12</a></td><td>January 13, 2020</td></tr>

RELEASE-NOTES.md

@@ -1,3 +1,16 @@
+# Rhino 1.7.15
+## May 3, 2024
+
+Highlights of this release include:
+
+* Basic support for "rest parameters"
+* Improvements in Unicode support
+* "Symbol.species" implemented in many places
+* More correct property ordering in many places
+* And many more improvements and bug fixes
+
+This release includes committs from 29 different committers. Thanks to you all for your help!
+
 # Rhino 1.7.14
 ## January 6, 2022