docs: Update Changelog and also document command line usage (#67)

* docs: Update Changelog and also document command line usage

* typos & white list

* hmpf

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+# Running Argo CD Image Updater
+
+The `argocd-image-updater` provides some command line parameters to control the
+behaviour of its operations. The following is a list of available parameters
+and their description.
+
+## Command "version"
+
+### Synopsis
+
+`argocd-image-updater version`
+
+### Description
+
+Prints out the version of the binary and exits.
+
+## Command "run"
+
+### Synopsis
+
+`argocd-image-updater run [flags]`
+
+### Description
+
+Runs the Argo CD Image Updater, possibly in an endless loop.
+
+### Flags
+
+**--argocd-auth-token *token* **
+
+Use *token* for authenticating to the Argo CD API. This token must be a base64
+encoded JWT, as generated by Argo CD.
+
+The token can also be set using the *ARGOCD_TOKEN* environment variable.
+
+**--argocd-grpc-web**
+
+If this flag is given, use the gRPC-web protocol to connect to the Argo CD API.
+This can be useful if your Argo CD API is behind a proxy that does not support
+HTTP/2, or only accept HTTP/2 on the front end.
+
+Can also be set using the *ARGOCD_GRPC_WEB* environment variable.
+
+**--argocd-insecure**
+
+If specified, the certificate of the Argo CD API server is not verified. Useful
+if you are using a self-signed TLS certificate for the Argo CD API server. As
+the name implies, this is an *insecure* setting and should not be used for
+production systems.
+
+Can also be set using the *ARGOCD_INSECURE* environment variable.
+
+**--argocd-plaintext**
+
+If specified, use an unencrypted HTTP connection to the ArgoCD API instead of
+TLS.
+
+Can also be set using the *ARGOCD_PLAINTEXT* environment variable.
+
+**--argocd-server-addr *server address* **
+
+Connect to the Argo CD API server at *server address*. *server address* must
+be a valid IP address or DNS host name, optionally with a port specification
+delimited using a colon, i.e. *10.23.42.5* or *argocd-server.argocd:8080*.
+If no port given, the protocol default will be used: Port 80 for plaintext
+connections, and port 443 for TLS connections.
+
+Can also be set using the *ARGOCD_SERVER* environment variable.
+
+**--disable-kubernetes**
+
+If running locally, and you do not have a working connection to any Kubernetes
+cluster, this flag will prevent Argo CD Image Updater from creating a client
+to interact with Kubernetes. When Kubernetes access is disabled, pull secrets
+for images can only be specified from an environment variable.
+
+**--dry-run**
+
+If this flag is set, Argo CD Image Updater won't actually perform any changes
+to workloads it found in need for upgrade.
+
+**--health-port *port* **
+
+Specifies the local port to bind the health server to. The health server is
+used to provide health and readiness probes when running as K8s workload.
+Use value *0* for *port* to disable launching the health server.
+
+**--interval *duration* **
+
+Sets the interval for checking whether there are new images available to
+*duration*. *duration* must be given as a valid duration identifier with
+a unit suffix, i.e. `2m` for 2 minutes or `30s` for 30 seconds. If no unit
+is given, milliseconds will be assumed. If set to `0`, ArgoCD Image Updater
+will exit after the first run, effectively disabling the interval. Default
+value is `2m0s`.
+
+**--kubeconfig *path* **
+
+Specify the Kubernetes client config file to use when running outside a
+Kubernetes cluster, i.e. `~/.kube/config`. When specified, Argo CD Image
+Updater will use the currently active context in the configuration to connect
+to the Kubernetes cluster.
+
+**--loglevel *level* **
+
+Set the log level to *level*, where *level* can be one of `trace`, `debug`,
+`info`, `warn` or `error`.
+
+**--match-application-name *pattern* **
+
+Only process applications that have a valid annotation and matches the given
+*pattern*. The *pattern* is a simple glob pattern and supports file system
+style wildcards, i.e. `*-staging` would match any application name with a
+suffix of `-staging`. Can be specified multiple times to define more than
+one pattern, from which at least one has to match.
+
+**--max-concurrency *number* **
+
+Process a maximum of *number* applications concurrently. To disable concurrent
+application processing, specify a number of `1`.
+
+**--once**
+
+A shortcut for specifying `--check-interval 0 --health-port 0`. If given,
+Argo CD Image Updater will exit after the first update cycle.
+
+**--registries-conf-path *path* **
+
+Load the registry configuration from file at *path*. Defaults to the path
+`/app/config/registries.conf`. If no configuration should be loaded, and the
+default configuration should be used instead, specify the empty string, i.e.
+`--registries-conf-path=""`.