Add almalinux-devtoolset11 image

[vweevers]

As alternative to centos7-devtoolset7 which:

• No longer builds (because mirrorlist.centos.org is offline)
• Doesn't support Node.js >= 18
• Doesn't support C++ 20
• Ships an EOL python version (3.6.8) which doesn't work with node-gyp 10

Ref: prebuild/prebuildify-cross#13
Ref: Level/classic-level#103 (comment)

[vweevers]

Test run: https://github.com/prebuild/docker-images/actions/runs/11430012950

[vweevers]

New test run: https://github.com/prebuild/docker-images/actions/runs/11430109669

[vweevers]

That's better:

> Run docker run --rm prebuild/almalinux-devtoolset11:dev node -v
  docker run --rm prebuild/almalinux-devtoolset11:dev node -v
  docker run --rm prebuild/almalinux-devtoolset11:dev npm -v
  docker run --rm prebuild/almalinux-devtoolset11:dev npx -v
  docker run --rm prebuild/almalinux-devtoolset11:dev python --version
  docker run --rm prebuild/almalinux-devtoolset11:dev npm ls node-gyp -g
  shell: /usr/bin/bash -e {0}
v18.20.4
10.7.0
10.7.0
Python 3.11.9
/usr/lib
`-- [email protected]
  +-- @npmcli/[email protected]
  | `-- [email protected] deduped
  `-- [email protected]