Possibility to use .npmrc instead of bunfig.toml

[carlosmfreitas2409]

Today, when we define a registry-url the action creates the Bun configuration file (bunfig.toml).

However, some actions still do not support this file, only .npmrc. And they may not even add it, since many of them have already been deprecated or are no longer maintained.

An example of this need is to publish libraries, more specifically using the changeset action.
This action does several things, the main one being publishing a library to NPM with the npm publish command and this script uses .npmrc.

I know there is the bun publish command, which supports bunfig and npmrc, however, this action (as well as others) does not have a variable for me to send the package manager I want. I also know that the correct thing would be for the action to have this support, but many actions are no longer maintained to add this.

So the idea of this issue is that the Bun action has a property that allows you to choose between bunfig and npmrc or even create both, without the need for a parameter.

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Another requirement is that both files are created in a temporary repository of the action, because if you do a push after the bun setup step, the files will be pushed (and should not).

And finally, authentication with npmrc, I believe that this setup-node file can be a good reference.