Add docs for Confidential Asset Contracts & SDK (#939)

* [docs] added docs for confidential asset contracts & sdk

* sdk docs fixes

* added links

* refactor: confidential asset guide and method descriptions

* typos

* typo

* refactor: update references from confidentialCoin to confidentialAsset in SDK documentation

* update links

* update link

* fix link

* update link

* update

---------

Co-authored-by: dovgopoly <idovgopoly@gmail.com>
Co-authored-by: lukachi <lukachisama@gmail.com>
Co-authored-by: zhoujun.ma <zhoujun@aptoslabs.com>

Author: 4 people

apps/nextra/pages/en/build/sdks/ts-sdk/_meta.tsx

@@ -29,4 +29,7 @@ export default {
   "legacy-ts-sdk": {
     title: "Legacy TypeScript SDK (Deprecated)",
   },
+  "confidential-asset": {
+    title: "Confidential Asset (CA)",
+  },
 };