fix(vscode): chat panel display issues

[wwayne]

Notable changes

• Left side icon
• Static content display (see the screenshots below)
• Fix the issue: setup token or other configuration makes the page empty
  • How to reproduce: open chat -> close chat -> change config -> re-open chat
  • Why: when webview invisible, the webview.postMessage actually won't work, we need webview.postMessage to init our chat page, so I add an listener to the visibility, and add init event when visible, if the webview is already inited, sending init event won't break the page

Before user setup the server, previously this page is empty

After connection, the config changed and somehow the chat panel is unavailable

[wsxiaoys]

let's use the version with background to enable better circle avatar display

[wsxiaoys]

or you can add background color with css

[wwayne]