Add option to enable http registry connections (#482)

Signed-off-by: Keith Zantow <kzantow@gmail.com>

README.md

@@ -204,6 +204,9 @@ registry:
   # skip TLS verification when communicating with the registry
   # SYFT_REGISTRY_INSECURE_SKIP_TLS_VERIFY env var
   insecure-skip-tls-verify: false
+  # use http instead of https when connecting to the registry
+  # SYFT_REGISTRY_INSECURE_USE_HTTP env var
+  insecure-use-http: false
 
   # credentials for specific registries
   auth: