add cli tool

similar to terser

minimal version

```sh
#! /usr/bin/env node

var {minify} = require('dts-minify').createMinifier(require('typescript'));
var fs = require('fs');
var {argv} = process;

if (argv[2] == '-w')
for (var f of argv.slice(3)) {
console.log(f);
fs.writeFileSync(f, minify(fs.readFileSync(f, 'utf8')), 'utf8');
}
else if (argv[2])
console.log(minify(fs.readFileSync(argv[2], 'utf8')));
else
console.log(minify(fs.readFileSync(0, 'utf8'))); // read stdin. fails on large inputs
```

No repository files or tests are named. Start by locating the current minifier entry point and the project's CLI configuration, then compare the minimal Node.js example in the issue. Done means a CLI handles a file, stdin, and the -w file-list mode described there.

Written by the indexing model from the issue text.