Trim down bundle size / Code splitting

[mirka]

Try

• stop using the DllPlugin altogether Code splitting (Part 0): Remove DLL #941
• load moment.js without the locale support Code splitting (Part 1): Drop locale support in moment.js #942
• dynamically load jszip Code splitting (Part 2): Dynamically load highlight.js and JSZip #943
• dynamically load highlight.js when markdown preview triggered and code block exists Code splitting (Part 2): Dynamically load highlight.js and JSZip #943
  • This chunk is currently 578 KB minified and loading the full library, which contains syntax rules for 176 languages and 82 styles. Core library is only 62 KB. Might be nicer if we just choose the common languages, and maybe add back more if we get requests.
• showdown Reduce app.js bundle to a reasonable size #1014
• draft.js Reduce app.js bundle to a reasonable size #1014

Current sizes (minified)

    vendors~jszip.js   93.6 KiB
vendors~highlight.js    539 KiB
              app.js   1.29 MiB

Original sizes (minified)

vendor.dll.js  1.58 MiB
       app.js   571 KiB