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/related.toml

@@ -0,0 +1,8 @@
+includeNewer = true
+threshold    = 60
+toLower      = false
+
+indices = [
+    { name = "tags", weight = 100 },
+    { name = "categories", weight = 200 },
+]