Update man page of manifest add

Ensure all the flags are covered by the man page.

Signed-off-by: Flavio Castelli <fcastelli@suse.com>

docs/source/markdown/podman-manifest-add.1.md

@@ -33,6 +33,25 @@ the image.  If *imageName* refers to a manifest list or image index, the
 architecture information will be retrieved from it.  Otherwise, it will be
 retrieved from the image's configuration information.
 
+**--authfile**=*path*
+
+Path of the authentication file. Default is ${XDG\_RUNTIME\_DIR}/containers/auth.json, which is set using `podman login`.
+If the authorization state is not found there, $HOME/.docker/config.json is checked, which is set using `docker login`. (Not available for remote commands)
+
+Note: You can also override the default path of the authentication file by setting the REGISTRY\_AUTH\_FILE
+environment variable. `export REGISTRY_AUTH_FILE=path`
+
+**--cert-dir**=*path*
+
+Use certificates at *path* (\*.crt, \*.cert, \*.key) to connect to the registry.
+Default certificates directory is _/etc/containers/certs.d_. (Not available for remote commands)
+
+**--creds**=*creds*
+
+The [username[:password]] to use to authenticate with the registry if required.
+If one or both values are not supplied, a command line prompt will appear and the
+value can be entered.  The password is entered without echo.
+
 **--features**
 
 Specify the features list which the list or index records as requirements for
@@ -50,6 +69,10 @@ configuration information.
 Specify the OS version which the list or index records as a requirement for the
 image.  This option is rarely used.
 
+**--tls-verify**
+
+Require HTTPS and verify certificates when talking to container registries (defaults to true). (Not available for remote commands)
+
 **--variant**
 
 Specify the variant which the list or index records for the image.  This option