Expose types for plugin's main function

[Milly]

Exposes the type PluginMain for the plugin's main function.
Update the way to define the main function of the plugin as follows:

// New approach
export const main: PluginMain = (denops) => {
  // ...
};

There is a discussion in #332 about extending the definition of the plugin's main function.

[Λlisue (Ali sue・ありすえ)]

Actually, I usually prefer ordinal function style but the new approach has a big advantage so I'm positive to change the style.

What we need to updates are

• denops.vim - #347
• deno-denops-core - vim-denops/deno-denops-core#7
• deno-denops-std - vim-denops/deno-denops-std#245
• denops-helloworld.vim - vim-denops/denops-helloworld.vim#16
• denops-maze.vim - vim-denops/denops-maze.vim#1
• denops-documentation - vim-denops/denops-documentation#13

[Λlisue (Ali sue・ありすえ)]

Moreover, I believe there are more suitable names than "PluginMain" for the following reasons:

• Developers are already aware that it's a plugin, hence the "Plugin" prefix seems somewhat redundant.
• Although the function is named "main," it merely serves as a placeholder and doesn't elucidate the functionality. Therefore, the type name should offer a more descriptive insight.

Considering the aforementioned points, I suggest "Entrypoint" as the type name. What are your thoughts?

[Milly]

I suggest "Entrypoint" as the type name. What are your thoughts?

Very good. I agree.

[Λlisue (Ali sue・ありすえ)]

Now denops_std (v6.5.0) serve Entrypoint and we can define the main function like

import type { Entrypoint } from "https://deno.land/x/denops_std@v6.5.0/mod.ts";

export const main: Entrypoint = (denops) => {
  // ...
};