error[preamble-re-description-colon]: preamble header `description` should not contain `:`
 --> input.md:4:13
  |
4 | description: This: proposal is a sample that should be considered
  |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ prohibited pattern was matched
  |
  = info: the pattern in question: `:`
error[preamble-re-title-colon]: preamble header `title` should not contain `:`
 --> input.md:3:7
  |
3 | title: "A sample: proposal"
  |       ^^^^^^^^^^^^^^^^^^^^^ prohibited pattern was matched
  |
  = info: the pattern in question: `:`