Update README and README_CN to document supported features and helper APIs

[wnagchi]

Motivation

• Clarify and document the framework's current capabilities by matching README content to the actual source implementation.
• Provide concrete usage examples for router guards, page-level route interception, helper APIs and the canvas wrapper to help developers integrate the library correctly.

Description

• Updated readme.md and readme_CN.md to reflect supported features and to add usage examples for $toPath route guards ($toPathBefore / $toPathBeforeAsync) and page-level $beforeRouter interception.
• Reworked and replaced outdated sections with current source-level helper APIs such as $setTimeFn, $animateStart, $call, $backPage, $getHeight, $getNode, $getWxImg, isIphoneX / getNav, WXML helpers ($onTab, $selectItem) and utility helpers ($random, $cutArray, $dataToString, $shinglier, $strSm).
• Documented canvas usage by adding an example for AniCanvas and clarified that $setStore / $getStore are available on Page/Component instances in addition to the constructor API.
• Cleaned up English and Chinese READMEs to remove stale store-min build instructions and to align examples with the current source modules.

Testing

• No automated tests were executed because this change is documentation-only and does not modify runtime code.

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Codex Task