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/params.toml

@@ -0,0 +1,37 @@
+mainSections   = ["post"]
+rssFullContent = true
+favicon        = ""
+
+[footer]
+    since = 2020
+
+[dateFormat]
+    published   = "Jan 02, 2006"
+    lastUpdated = "Jan 02, 2006 15:04 MST"
+
+[sidebar]
+    emoji    = "🍥"
+    subtitle = "Lorem ipsum dolor sit amet, consectetur adipiscing elit."
+    [sidebar.avatar]
+        enabled = true
+        local   = true
+        src     = "img/avatar.png"
+
+[article]
+    [article.license]
+        enabled = true
+        default = "Licensed under CC BY-NC-SA 4.0"
+
+[widgets]
+    homepage = [
+        { type = "search" },
+        { type = "archives", params = { limit = 5 } },
+        { type = "categories", params = { limit = 10 } },
+        { type = "tag-cloud", params = { limit = 10 } },
+    ]
+    page = [{ type = "toc" }]
+
+[comments]
+    # See complete configuration in config/_default/params.toml
+    enabled  = true
+    provider = "disqus"