add example on how to customize mathjs

Author: Cube707

exampleVault/.obsidian/plugins/js-engine/data.json

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+{
+  "startupScripts": [
+    "mathJScustomisation.js"
+  ]
+}

exampleVault/Advanced Examples/Customising math-views.md

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+---
+num: 5
+---
+
+You may find yourself wanting to add functionality to the math-view elements. This file will show you some tricks how you can achieve that.
+
+## Importing new options into mathJS
+
+The math-views internal use the [mathJS](https://mathjs.org/) libary, which allows the user to define his own functions and constants, as described in [their documentation](https://mathjs.org/docs/core/extension.html).
+
+To leverage that, Meta Bind exposed its mathjs instance for you to modify. The most sensible place to do this, is inside a JS-Engine startup-script. This ensures the modifications are loaded early and will be immediately available when the first documents gets rendered.
+
+> [!warning]
+> Moddifying mathJS via a js-engine codeblock inside a document may cause timing problems and is not recomended!
+
+
+### Using a custom function `clamp`
+
+As an example, we defined the `clamp()` function, which is not part of default mathJS, but can be very helpful.
+It takes in three parameters, the current value, a minimum and a maximum. It returns the current value as long as its inside the range otherwise the boundary-value.
+
+```js
+clamp:  (val, min, max) => Math.min(Math.max(min, val), max)
+```
+
+As long as `mathJScustomisation.js` is loads as a startup-script, we can now use this function in any math-view, like shown in this example:
+
+This is a clamped value: `VIEW[clamp({num}, 0, 10)][math]` actual value: `VIEW[{num}][math]`
+Test it with the slider
+
+```meta-bind
+INPUT[slider(minValue(-5),maxValue(15),addLabels):num]
+```
+

exampleVault/mathJScustomisation.js

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+const mb = engine.getPlugin('obsidian-meta-bind-plugin').api;
+
+// the following shows how to customize meta-binds mathjs
+mb.mathJSimport({
+	// we define the function 'clamp'
+	clamp:  (val, min, max) => Math.min(Math.max(min, val), max),
+});