Need of extra volume mount for sidecar container

[hyffrank]

The injected sidecar container now contains only one "emptyDir" which is used to share data between containers inside pods. One requirement is that when user define output module of Fluentd/FluentBit as "File", extra volume mount could be defined in annotation so that the injector could assign these volume mounts for sidecar to use.

Expected behavior:
Putting annotation [fluentd-sidecar-injector.h3poteto.dev/extra-volumemount: 'my_mount'] and [fluentd-sidecar-injector.h3poteto.dev/extra-mountpath: '/var/log/app'] on manifest results in below volumemount in sidecar:

spec:
volumeMounts:
- name: my_mount
mountPath: /var/log/app