Manipulator: Add JSON parse support (#35077)

Support parsing JSON from each component's main element using the `data-bs-config` attribute.

The `bs-config` attribute will be reserved and omitted during `getDataAttributes` parsing.

With this commit, every component, will create its config object, using:

* defaults
* data-bs-config
* the rest of data attributes
* configuration object given during instance initialization

Co-authored-by: XhmikosR <xhmikosr@gmail.com>
Co-authored-by: Mark Otto <markd.otto@gmail.com>
Co-authored-by: Mark Otto <markdotto@gmail.com>

js/src/util/config.js

@@ -38,8 +38,11 @@ class Config {
   }
 
   _mergeConfigObj(config, element) {
+    const jsonConfig = isElement(element) ? Manipulator.getDataAttribute(element, 'config') : {} // try to parse
+
     return {
       ...this.constructor.Default,
+      ...(typeof jsonConfig === 'object' ? jsonConfig : {}),
       ...(isElement(element) ? Manipulator.getDataAttributes(element) : {}),
       ...(typeof config === 'object' ? config : {})
     }