[FEATURE] CellWriter.at should support a list of cells as assigment

[rhazn]

User Story

1. As a {user}
2. I want {to write into multiple non-adjacent files}
3. So that {I can replace multiple values at once}

User Acceptance Criteria

• [ ] Users can assign a list of cells to CellWriter.at

Examples

block ExampleWriter oftype CellWriter {
  at: [cell A1, cell M1];
  write: ["name1", "name2"];
}

Notes

• could also be done by changing the cell range syntax (maybe cells A1, M1?)

Definitions of Done

• [ ] A PR has been opened and accepted
• [ ] All user acceptance criteria are met
• [ ] All tests are passing

[rhazn]

Controversial suggestion (that seems to small for a RFC), what do you think @felix-oq , @georg-schwarz ?