update the spec change log with changes from v3.0.13 (#910)

* update the spec change log with changes from v3.0.13

* add related GitHub PRs to the change log

Author: bashbaug

api/appendix_e.asciidoc

@@ -561,3 +561,12 @@ Changes from *v3.0.12*:
   * Added missing calls to {clBuildProgram} to the `cl_khr_command_buffer` and `cl_khr_command_buffer_mutable_dispatch` sample code.
   * Fixed a copy-paste error in the extensions quick reference appendix.
   * Fixed typos and improved formatting consistency in the extensions spec.
+
+Changes from *v3.0.13*:
+
+  * Corrected the precision for `cross` and `dot` to be based on `HALF_EPSILON` in `cl_khr_fp16`, see GitHub #893.
+  * Added a context query for command-buffers to `cl_khr_command_buffer`, see GitHub #899.
+  * Updated the semaphore wait and signal rules for binary semaphores in `cl_khr_semaphore`, see GitHub #882.
+  * Removed redundant error conditions from `cl_khr_external_semaphore` and `cl_khr_external_memory`, see GitHub #903 and #904.
+  * Added new extension:
+      ** `cl_khr_command_buffer_multi_device` (provisional)