Update Dockerfile to Fedora 34

Add readme to not forget how to build/deploy.

Change-Id: Ibe274973b873b8e5c699f9c2ffa4cb0745a7f93f
Signed-off-by: Alexander Kurtakov <akurtako@redhat.com>
Reviewed-on: https://git.eclipse.org/r/c/linuxtools/org.eclipse.linuxtools/+/188863
Tested-by: Linux Tools Bot <linuxtools-bot@eclipse.org>
diff --git a/releng/container-build/Dockerfile b/releng/container-build/Dockerfile
index ccb840a..da58d2f 100644
--- a/releng/container-build/Dockerfile
+++ b/releng/container-build/Dockerfile
@@ -1,4 +1,4 @@
-FROM eclipsecbi/fedora-gtk3-mutter:33-gtk3.24
+FROM eclipsecbi/fedora-gtk3-mutter:34-gtk3.24
 
 # Back to root for install
 USER 0
diff --git a/releng/container-build/README.md b/releng/container-build/README.md
new file mode 100644
index 0000000..4cd13db
--- /dev/null
+++ b/releng/container-build/README.md
@@ -0,0 +1,23 @@
+Steps to deploy:
+
+* Build:
+
+```
+podman build -t USER_NAME/linuxtools-build-test-dependencies .
+```
+
+* Login
+
+```
+podman login docker.io
+```
+
+* Deploy
+
+```
+podman push docker.io/USER_NAME/linuxtools-build-test-dependencies
+```
+
+**Note:**
+
+USER_NAME in various configs is 'akurtakov' now. If new image is published by another user this has to be changes in various Jenkins files and configs.
\ No newline at end of file