add usage page for startup-scripts

Author: Cube707

src/content/docs/guides/startupscripts.md

@@ -0,0 +1,29 @@
+---
+title: Startup-Scripts
+description: A guide on how to use startup-scripts.
+---
+
+JS-Engine supports startup-scripts, similar to the CSS-snippets from Core-Obsidian.
+
+You can select the script-file you want to use as startup-scripts and JS-Engine will run them for you when never Obsidian starts up.
+
+:::note
+Different from Core-Obsidian, JS-Engine startup-scripts can not be stored inside the `.obsidian/` folder.
+They need to be somewhere inside your vault.
+:::
+
+## Configuring Startup-Scripts
+
+You can configure which files you want to have run from JS-Engines settings tab.
+There you will see a list of all JavaScript files detected inside the vault and
+you can enable the ones you want to run at startup.
+
+### Setting a folder for startup-scripts
+
+To reduce the list of shown files you can define the name of a folder you use to store your scripts.
+JS-Engine will only check that folder and only list files inside it as options.
+
+## Global Variables
+
+JS-Engine runs the scripts in the same context as all other code-blocks.
+So the available global variable are the same and can be found [here](/obsidian-js-engine-plugin-docs/api/classes/api/).