Changes for releasing 1.13 (#2070)

* Changes for releasing 1.13

- Changed release version in charts 1.13
- Made changes in release scripts and makefile

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

* Update helm chart maintainers

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

charts/fission-core/values.yaml

@@ -17,7 +17,7 @@ repository: index.docker.io
 image: fission/fission-bundle
 
 ## Fission image version
-imageTag: 1.12.0
+imageTag: 1.13.0
 
 ## Image pull policy
 pullPolicy: IfNotPresent
@@ -43,7 +43,7 @@ fetcher:
   ## Fetcher repository
   image: fission/fetcher
   ## Fetcher image version
-  imageTag: 1.12.0
+  imageTag: 1.13.0
 
   ## Fetcher is only for to downloading or uploading archive.
   ## Normally, you don't need to change the value here, unless necessary.