Migrate documentation from doc to docs directory and switch to ex_doc

Author: zhongwencool

.gitignore

@@ -2,6 +2,7 @@
 .tool-versions
 _build
 deps
+doc
 elvis
 *.o
 *.beam

LICENSE

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2015 某文<zhongwencool@gmail.com>
+Copyright (c) 2015-2025 某文<zhongwencool@gmail.com>
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -0,0 +1,30 @@
+[
+  extras: [
+    {"README.md", title: "Home"},
+    "./docs/plugin.md",
+    "./docs/changlog.md",
+    "LICENSE"
+  ],
+  logo: "./docs/favicon.png",
+  authors: [
+    "Zhongwen Deng <zhongwencool@gmail.com>"
+  ],
+  main: "readme",
+  source_url: "https://github.com/zhongwencool/observer_cli",
+  homepage_url: "https://github.com/zhongwencool/obsever_cli",
+  with_mermaid: true,
+  before_closing_body_tag: fn
+    :html ->
+      """
+      <script src="https://cdn.jsdelivr.net/npm/mermaid/dist/mermaid.min.js"></script>
+      <script>mermaid.initialize({startOnLoad: true})</script>
+      """
+
+    _ ->
+      ""
+  end,
+  api_reference: false,
+  warnings_as_errors: true,
+  groups_for_docs: [],
+  filter_modules: fn _, _ -> false end
+]