Support bracket notation for repeated messages "[{}]".
Example:
$ echo "value: [{}]" | fmt
parser.Format for path <stdin> with content "value: [{}]\n" returned err
[{}] notation not supported
Full error: parser failed to make progress at index 8
position {Byte:8 Line:1 Column:9}
before: "value: ["
after: "{}]"
before+after: "value: [{}]"
1 error(s) encountered during execution
Support bracket notation for repeated messages "[{}]".
Example: