ref: adopt vscode's styling in beginner tips page

[Eskibear]

• use vscode-webview-ui-toolkit

[Eskibear]

demo:

[Eskibear]

@jdneo @CsCherrYY please help to take a look or play with the PR build, verify if it's working well.

[CsCherrYY]

just my own opinion, I just zoom in once than the default zoom in my PC (2k resolution), the font size of current version is a little small and a little hard to read many words in a page. The marketplace version has a gray background so it may look better. Can we consider increasing the font size?

[Eskibear]

now:

code {
    font-family: var(--vscode-editor-font-family);
}