Signaling JavaScript 2.1.5 SDK

[HeatherWYL]

Please find EN docs in the following links:

• Release notes: https://github.com/AgoraIO/shengwang-doc-source/blob/master/docs/rtm2/overview/_release-notes-en.javascript.mdx
• API reference: https://github.com/AgoraIO/shengwang-doc-source/tree/master/docs-api-reference/rtm2/_en/_javascript
• Common fragments:
  • https://github.com/AgoraIO/shengwang-doc-source/tree/master/shared/rtm2/_rtmstatus-en.mdx
  • https://github.com/AgoraIO/shengwang-doc-source/tree/master/shared/rtm2/_stateitem-en.mdx

We also add the FAQ in CN site: https://doc-internal.shengwang.cn/doc-new/rtm/doc/rtm2/javascript/rtm2-integration-issue