feat: initial implementation of hubmanager v0.1.0

Add a Bash CLI tool to manage Docker Registry images remotely.
Supports Docker Hub and self-hosted Docker Registry v2 API with
automatic auth detection (bearer token or HTTP basic auth).

Subcommands: login, list, tags, inspect, delete, copy, prune
Dependencies: curl, jq, bash 4+

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.editorconfig

@@ -0,0 +1,12 @@
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+[*]
+indent_style = space
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = false
+insert_final_newline = false