feat!: adds Ruby 4.0 support

[timbru31]

This pull request updates the project to add support for Ruby 4.0 and removes support for the Ruby 3.5 release candidate across all Docker images, CI workflows, and documentation. The changes ensure that all build, lint, and test processes now target Ruby versions 3.2, 3.3, 3.4, and 4.0, in combination with Node.js 20, 22, and 24.

Key changes include:

Ruby version support and Dockerfiles:

• All Dockerfiles for the 3.5 (RC) Ruby version have been renamed and updated to use 4.0 as the base image, across all Node.js and variant combinations (default, slim, alpine). ([[1]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-6a27116950d4bfcb2f666f69f677654603f260aae0390969da01437d3b97c311L1-R1), [[2]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-9a91a1cf9261e606979dd252f158163010d9aa19fd7caa2c477c86d04a68178cL1-R1), [[3]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-6e45ef2276af51e277bcc8299c25d5ebccb5d5e33dcbfc506f6a3910edfde740L1-R1), [[4]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-1bfce8c4d96621cba297e72b6c3e8c11f4605ea0a07213fd045dd92ed1972403L1-R1), [[5]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-ec4324f37eb578f46f7cc5a76e34da7525b72ddc7bc9a399c88f996693292f83L1-R1), [[6]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-fbb70a02d589048078eeca2eeb9952f6c9932e5e27edd4f55394883ad8fa958dL1-R1), [[7]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-58398f443f100a5167aca288cf04dcc67426a43a31b427d4be102c2c9dd76004L1-R1), [[8]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-eb480bfb61fb5f9d40b37abbf2e551700adf57cf9e7a00999491d12eaf4bfa12L1-R1), [[9]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-989a34f342f1a9fddadd2367fe28036f07d0854f94379874724e5fd17915cde7L1-R1))

CI/CD workflow updates:

• Updated the Ruby version matrix in .github/workflows/buildx.yml, .github/workflows/dockerimage.yml, and .github/workflows/hadolint.yml to include 4.0 and remove 3.5. ([[1]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-adb76474a4d21f08634f1141bb92786577a2cca214bc43ea65ebff9b578ea2e2L17-R17), [[2]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-e33bc21aa610231bb3b9c0516d58cd5c53cf2e57ac1f8ee536492488d2f00b4aL16-R16), [[3]](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-93a1f172ec6e4110cd725d72be37e9f155cffa1b2470bcdaa99bb49cfa2201d1L18-R19))
• Changed the tagging logic in the build workflow to use Ruby 4.0 and Node.js 24 as the basis for the latest Docker tag. ([.github/workflows/buildx.ymlL55-R55](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-adb76474a4d21f08634f1141bb92786577a2cca214bc43ea65ebff9b578ea2e2L55-R55))

Documentation:

• Updated README.md to reflect Ruby 4.0 support and remove mention of Ruby 3.5 (RC). ([README.mdL1-R11](https://github.com/timbru31/docker-ruby-node/pull/760/files#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5L1-R11))