feat: add npm for js dependencies + move src/ files to root folder

- add node service in docker-compose.yml
- update .devcontainer Dockerfile by adding node, npm and vim
- init package.json for npm with tailwindcss, postcss, commitlint and commitizen as dev dependencies
- update default layout main header and footer
- replace CI's welcome_message.php with home.php listing all podcasts
- add AUTHORS.md file
- add docs folder in which to place castopod's technical documentation

.devcontainer/devcontainer.json

@@ -1,16 +1,18 @@
 // For format details, see https://aka.ms/vscode-remote/devcontainer.json or this file's README at:
 // https://github.com/microsoft/vscode-dev-containers/tree/v0.117.1/containers/docker-existing-dockerfile
 {
-	"name": "Existing Dockerfile",
-	"dockerFile": "./Dockerfile",
-	"settings": {
-		"terminal.integrated.shell.linux": null
-	},
-	"extensions": [
-		"mikestead.dotenv",
-		"bmewburn.vscode-intelephense-client",
-		"streetsidesoftware.code-spell-checker",
-		"naumovs.color-highlight",
-		"heybourn.headwind"
-	]
-}
+  "name": "Existing Dockerfile",
+  "dockerFile": "./Dockerfile",
+  "settings": {
+    "terminal.integrated.shell.linux": null
+  },
+  "extensions": [
+    "mikestead.dotenv",
+    "bmewburn.vscode-intelephense-client",
+    "streetsidesoftware.code-spell-checker",
+    "naumovs.color-highlight",
+    "heybourn.headwind",
+    "anish-m.ci-snippets2",
+    "wayou.vscode-todo-highlight"
+  ]
+}