Tdewolff-minify

- CSS: fix `import url(` early-termination and `import url( )`
- HTML: keep space after empty phrasing elements, fixes 427
- JS: fix switch statement optimization, fixes 426
- JS: remove if statement if if-block is empty, fixes 428

- JS: fix parsing of `a++==b`
- CSS: fix bug in early-terminated `import url(`

- Revert incorporating the parse dependency into this repository from the previous release
- cmd: Bash completion support for zsh, fixes 421
- JS: fix {a:b=1} when inside arrow function parameter list, fixes 422

- Incorporate the `parse` dependency into this repository
- cmd: fix forward/backward slash for Windows platform, fixes 403
- JS: add space to `a<!--b` and `a</script>/` in more instances to avoid confusion with operators, see 413
- JS: add variable scope to switch statement
- JS: parse `async(a)` as possible expression or arrow func, fixes 406
- JS: fix lexical variable renaming for descoped, fixes 405
- JS: fix import statement/call parsing at module level, fixes 399
- JSON: add `KeepNumbers` option, fixes 400

- keep minimal Go version at 1.13 (and not 1.16 which is more convenient for cmd)
- cmd: fix regression for stdin/stdout, fixes 392
- HTML: update error line and column for errors from other minifiers
- CSS: KeepCSS2 (for IE11) doesn't use initial for background-color, fixes 394
- CSS: keep integers for z-index even in functions such as calc, fixes 395
- CSS: fix minify to initial/auto/none for flex, fixes 398

- JS: accept shebang comment as first line, fixes 345
- HTML: update fix for space after `<i></i>`, see 390
- CSS: unicode-range minification, fixes 321 and closes 344