OIDC + Slack Token for `nodejs/doc-kit`

[avivkeller]

Ref: nodejs/doc-kit#624

doc-kit needs:

• A SLACK_TOKEN to publish alerts in Slack (cc @bensternthal)
• An OIDC token for @nodejs/doc-kit @node-core/doc-kit set up as follows:

cc @nodejs/TSC

[bensternthal]

@avivkeller what permissions does the slack app need? Is the below sufficent?

[bensternthal]

api key shared via slack

[legendecas]

The https://www.npmjs.com/~nodejs-foundation account has no access to https://www.npmjs.com/org/nodejs. The allowed namespace is https://www.npmjs.com/org/node-core.

[legendecas]

Skeleton package https://www.npmjs.com/package/@node-core/doc-kit with OIDC settings set up.