feat: add option for docker image rebuild (#878)

Adds option to rebuild local action docker images

Fixed up README due to missing flags after
PR #714 and #716

Signed-off-by: hackercat <me@hackerc.at>

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

pkg/runner/runner.go

@@ -29,6 +29,7 @@ type Config struct {
 	DefaultBranch         string            // name of the main branch for this repository
 	ReuseContainers       bool              // reuse containers to maintain state
 	ForcePull             bool              // force pulling of the image, even if already present
+	ForceRebuild          bool              // force rebuilding local docker image action
 	LogOutput             bool              // log the output from docker run
 	Env                   map[string]string // env for containers
 	Secrets               map[string]string // list of secrets