textproc/xt-rs: import package

xt is a cross-format translator for JSON, YAML, TOML, and MessagePack.

xt is built to do one thing well, and tries to maintain a minimal interface and
feature set.
The most common options are -t to specify an output format other than JSON, and
one or more files to read from rather than standard input.

Some of xt's notable features include:
- Automatic Format Detection
  When the input format is not specified with the -f option, xt can detect it
  automatically by file extension, or by examining the content of the input
  stream itself.
- Multi-Document Support
  With most output formats, xt can translate multiple input files, each
  containing one or more independent documents, to a single output stream.
  For example, a set of YAML files with documents separated by --- markers can
  translate to a single stream of newline-delimited JSON objects. With format
  detection enabled, xt can even translate input files in different formats to
  a single output.
- Streaming Translation
  xt can translate multi-document inputs from unbounded sources like shell
  pipes with minimal buffering, while still supporting features like automatic
  format detection. Streaming is enabled automatically whenever it's required.

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