Call `postcss` script with the correct ext on MS-Windows

[ikappaki]

Hi,

could you please consider a patch for teknql.tailwind to call the postcss script with the correct extension (.cmd) on MS-Windows.

Fixes issue #10.

Tested to work on MS-Windows:

> npx shadow-cljs watch ui
shadow-cljs - config: d:\clj\issues\issue-jit-windows\shadow-cljs.edn
shadow-cljs - socket connect failed, server process dead?
shadow-cljs - updating dependencies
shadow-cljs - dependencies updated
shadow-cljs - HTTP server available at http://localhost:3000
shadow-cljs - server version: 2.15.12 running at http://localhost:9630
shadow-cljs - nREPL server started on port 52844
shadow-cljs - watching build :ui
[:ui] Configuring build.
[:ui] Using default value for :tailwind/files.
[:ui] Using default value for :tailwind/config.
[:ui] Using default value for :postcss/config.
[:ui] Starting postcss process.
[:ui] Compiling ...

warn - You have enabled the JIT engine which is currently in preview.
warn - Preview features are not covered by semver, may introduce breaking changes, and can change at any time.

info - Tailwind CSS is watching for changes...
info - https://tailwindcss.com/docs/just-in-time-mode#watch-mode-and-one-off-builds
[:ui] Build completed. (118 files, 117 compiled, 0 warnings, 11.56s)

and the site.css file has been generated:

>d>dir resources\public\css\site.css
...
 Directory of D:\clj\issues\issue-jit-windows\resources\public\css

23/10/2021  21:36            14,308 site.css

Thanks

[rschmukler]

Finally got around to merging this! Thank you :+1: Live in v1