refactor: use TOML for configuration file (#1228)

* refactor: remove jsconfig.json

* chore: remove devcontainer config

* refactor: migrate Hugo configuration from `hugo.yaml` to dedicated `module.toml` and `params.toml` files, and update minimum Hugo version.

* refactor: migrate demo site configuration from `hugo.yaml` to `config/_default/*.toml`

* feat: enable local sidebar avatar for demo site and relocate its image to demo assets.

* feat: migrate demo site to Hugo Modules for theme management.

* fix: wrong config folder name

demo/config/_default/hugo.toml

@@ -0,0 +1,26 @@
+baseURL      = "https://example.com/"
+languageCode = "en-us"
+title        = "Example Site"
+copyright    = "Example Person"
+
+# Theme i18n support
+# Available values: ar, bn, ca, de, el, en, es, fr, hu, id, it, ja, ko, nl, pt-br, th, uk, zh-cn, zh-hk, zh-tw
+defaultContentLanguage = "en"
+
+# Set hasCJKLanguage to true if DefaultContentLanguage is in [zh-cn ja ko]
+# This will make .Summary and .WordCount behave correctly for CJK languages.
+hasCJKLanguage = false
+
+[[module.imports]]
+path = "github.com/CaiJimmy/hugo-theme-stack/v3"
+
+
+[pagination]
+    pagerSize = 3
+
+[permalinks]
+    post = "/p/:slug/"
+    page = "/:slug/"
+
+[services.disqus]
+    shortname = "hugo-theme-stack"