Improve Dockerfile (#256)

* Use npm ci over install to achive faster and more expectable build results;
Split copy package(-lock).json files and ci then to avoid reinstalling dependencies when not needed => Faster build times

* Stopp adding wasm type to mime.types, its already there (duplicate):
- avoids warning in console
- cleans up
- might have been missing in past nginx:alpine versions but now exists

* Change node tag from alpine and nginx to more specific ones for #260

.dockerignore

@@ -0,0 +1,2 @@
+node_modules/
+.git/