Create dprint plugin to format the PO files.

[HidenoriKobayashi]

Create a stable format plugin for PO files using dprint.

[HidenoriKobayashi]

The general direction for this task is

• create a dprint wasm plugin to format PO files
• use polib crate to parse the PO structure
• use textwrap if polib does not handle languages with no space

So far, I have

• created a plugin that uses polib and found that it doesn't handle languages with no space well. It essentially becomes one line.
• integrated textwrap to find the dprint complaining about the translation result not being stable.

Now, I'm developing some unit tests for the plug-in as the test harness checks the stability of the result by translating the result one more time. I also found that polib does not try to format long comment/source lines.

[HidenoriKobayashi]

I think I know why the result is not stable with textwrap. It removes the space when a line is broken at the space. For example,

msgid ""
"[![Build workflow](https://img.shields.io/github/actions/workflow/status/"
"google/comprehensive-rust/build.yml?style=flat-square)](https://github.com/"
"google/comprehensive-rust/actions/workflows/build.yml?query=branch%3Amain) [!"
"[GitHub contributors](https://img.shields.io/github/contributors/google/"
"comprehensive-rust?style=flat-square)](https://github.com/google/"
"comprehensive-rust/graphs/contributors)"

would be turned into

msgid ""
"[![Build workflow](https://img.shields.io/github/actions/workflow/status/google/"
"comprehensive-rust/build.yml?style=flat-square)](https://github.com/google/"
"comprehensive-rust/actions/workflows/build.yml?query=branch%3Amain) [![GitHub"
"contributors](https://img.shields.io/github/contributors/google/comprehensive-"
"rust?style=flat-square)](https://github.com/google/comprehensive-rust/graphs/"
"contributors)"

There's no space after "GitHub" in the third line. So if this result is fed into the formatter again, then it would produce a different result because it see "GitHubcontributors".

@mgeisler I think you were right when you suspected that this might be related to mgeisler/textwrap#503
Although it's slightly different in our case, because we just want to have one space?