docs: add docs and benchmarks to plot/vega/autosize/ctor

lib/node_modules/@stdlib/plot/vega/autosize/ctor/README.md

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+<!--
+
+@license Apache-2.0
+
+Copyright (c) 2026 The Stdlib Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+-->
+
+# Autosize
+
+> Autosize constructor.
+
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<!-- Package usage documentation. -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var Autosize = require( '@stdlib/plot/vega/autosize/ctor' );
+```
+
+#### Autosize( \[options] )
+
+Returns an autosize instance.
+
+```javascript
+var autosize = new Autosize();
+// returns <Autosize>
+```
+
+The constructor accepts the following `options`:
+
+-   **contains**: method for determining how a size calculation should be performed. Default: `'content'`.
+-   **resize**: boolean indicating whether to re-calculate an autosize layout on every view update. Default: `false`.
+-   **type**: autosize method. Default: `'pad'`.
+
+```javascript
+var autosize = new Autosize({
+    'contains': 'padding',
+    'resize': true,
+    'type': 'fit'
+});
+// returns <Autosize>
+
+var v = autosize.type;
+// returns 'fit'
+```
+
+* * *
+
+### Writable Properties
+
+<a name="prop-contains"></a>
+
+#### Autosize.prototype.contains
+
+Method for determining how a size calculation should be performed. Default: `'content'`.
+
+```javascript
+var autosize = new Autosize();
+
+// Set:
+autosize.contains = 'padding';
+
+// Get:
+var v = autosize.contains;
+// returns 'padding'
+```
+
+<a name="prop-resize"></a>
+
+#### Autosize.prototype.resize
+
+Boolean indicating whether to re-calculate an autosize layout on every view update. Default: `false`.
+
+```javascript
+var autosize = new Autosize();
+
+// Set:
+autosize.resize = true;
+
+// Get:
+var v = autosize.resize;
+// returns true
+```
+
+<a name="prop-type"></a>
+
+#### Autosize.prototype.type
+
+Autosize type. Default: `'pad'`.
+
+```javascript
+var autosize = new Autosize();
+
+// Set:
+autosize.type = 'none';
+
+// Get:
+var v = autosize.type;
+// returns 'none'
+```
+
+* * *
+
+### Read-only Properties
+
+<a name="prop-properties"></a>
+
+#### Autosize.prototype.properties
+
+List of enumerable properties.
+
+```javascript
+var autosize = new Autosize();
+
+var v = autosize.properties;
+// returns [ 'contains', 'resize', 'type' ]
+```
+
+* * *
+
+### Methods
+
+<a name="method-to-json"></a>
+
+#### Autosize.prototype.toJSON()
+
+Serializes an autosize instance to a JSON object.
+
+```javascript
+var autosize = new Autosize({
+    'type': 'fit'
+});
+
+var v = autosize.toJSON();
+// returns { 'contains': 'content', 'resize': false, 'type': 'fit' }
+```
+
+This method is implicitly invoked by `JSON.stringify`.
+
+```javascript
+var autosize = new Autosize({
+    'type': 'fit'
+});
+
+var str = JSON.stringify( autosize );
+// returns '{"contains":"content","resize":false,"type":"fit"}'
+```
+
+* * *
+
+### Events
+
+#### 'change'
+
+Emitted whenever a property value changes.
+
+```javascript
+var autosize = new Autosize();
+
+autosize.on( 'change', onChange );
+
+autosize.type = 'fit';
+
+function onChange( event ) {
+    console.log( 'Updated property: %s', event.property );
+}
+```
+
+</section>
+
+<!-- /.usage -->
+
+<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+</section>
+
+<!-- /.notes -->
+
+<!-- Package usage examples. -->
+
+<section class="examples">
+
+* * *
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var Autosize = require( '@stdlib/plot/vega/autosize/ctor' );
+
+var autosize = new Autosize();
+console.log( autosize.toJSON() );
+```
+
+</section>
+
+<!-- /.examples -->
+
+<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="references">
+
+</section>
+
+<!-- /.references -->
+
+<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
+
+<section class="related">
+
+</section>
+
+<!-- /.related -->
+
+<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="links">
+
+</section>
+
+<!-- /.links -->