Unhelpful documentation for runBuildScriptsCommand

[maghoff]

The configuration option runBuildScriptsCommand has the following documentation:

    /// Advanced option, fully override the command rust-analyzer uses to
    /// run build scripts and build procedural macros. The command should
    /// include `--message-format=json` or a similar option.

This documentation is just short of helpful. Including a default command line example would be a much better starting point for figuring out what to put in this configuration option. It looks like the default command line is: cargo check --quiet --workspace --message-format=json --all-targets plus optionally target and feature configuration. Maybe rewrite the doc comment to:

    /// Advanced option, fully override the command rust-analyzer uses to
    /// run build scripts and build procedural macros. The command should
    /// include `--message-format=json` or a similar option.
    ///
    /// By default, a cargo invocation will be constructed for the configured
    /// targets and features, with the following base command line:
    ///
    /// ```bash
    /// cargo check --quiet --workspace --message-format=json --all-targets
    /// ```