Add v1.8 change log, and update README.md.

Signed-off-by: Xun Jiang <jxun@vmware.com>

README.md

@@ -26,6 +26,7 @@ Below is a listing of plugin versions and respective Velero versions that are co
 
 | Plugin Version  | Velero Version |
 |-----------------|----------------|
+| v1.8.x          | v1.12.x        |
 | v1.7.x          | v1.11.x        |
 | v1.6.x          | v1.10.x        |
 | v1.5.x          | v1.9.x         |

changelogs/CHANGELOG-1.8.md

@@ -0,0 +1,9 @@
+## All changes
+
+  * Add Volume Project setting to support the scenario describe in issue #92 (#149, @blackpiglet)
+  * Add support for CSI driver gcp.csi.confidential.cloud (#146, @ps-occrp)
+  * Check the "SNAPSHOTS" quota on Google Cloud Platform and do not attempt to create snapshots if the quota is reached. (#144, @0x113)
+  * Add cross-project backup and restore functionality in the Velero GCP Plugin. (#143, @Savostov-Arseny)
+  * Disable blob signing initialization for non service account file based credentials (#142, @kaovilai)
+  * Bump Golang version to v1.20 and add push image to gcr.io in push action. (#138, @blackpiglet)
+  * Replace busybox with internal copy binary and fix CVEs. (#137, @blackpiglet)