feat: implement inlay hint configuration

[Myriad-Dreamin]

As discussed in #16, The full configuration items are list following, and some of them are not configurable by users:

pub struct InlayHintConfig {
    // positional arguments group
    pub on_pos_args: bool,
    pub off_single_pos_arg: bool,

    // variadic arguments group
    pub on_variadic_args: bool,
    pub only_first_variadic_args: bool,

    // todo
    // The typst sugar grammar
    pub on_content_block_args: bool,
}

impl InlayHintConfig {
    pub const fn smart() -> Self {
        Self {
            on_pos_args: true,
            off_single_pos_arg: true,

            on_variadic_args: true,
            only_first_variadic_args: true,

            on_content_block_args: true,
        }
    }
}

These configurations are not exposed yet though.