Emscripten: wrap generated html into a directory

[artificiel]

adds a layer so the emscripten product is packaged as:

bin/$APP_NAME/index.html

this makes it possible to directly upload the bin/APP_NAME directly on a server, and "implicitly" publish it as http://server.name/APP_NAME without renaming anything

(previous behaviour requires renaming the bin directory, and even then would still produce a redundant name such as http://server.name/APP_NAME/APP_NAME.html)

fix #7592

[ofTheo]

does the emrun command work as expected with this change?

ie: emrun bin/3DPrimitivesExample/index.html

edit:

I see you can do emrun bin/3DPrimitivesExample/
What about the data folder? does that get copied to bin/3DPrimitivesExample/ with this change?

[artificiel]

my (superficial) understanding is that bin/data dir gets processed into a .data file by the --preload-file option (which currently is a problem if there is no data directory present: #7593)

so I did just now:

% cd $OF_ROOT/examples/graphics/imageSubsectionExample
% emmake make 
% scp -r bin/imageSubsectionExample #####@varia.artificiel.org:/usr/www/of/
index.wasm                     100% 6537KB  47.5MB/s   00:00    
index.html                     100% 5370   574.5KB/s   00:00    
index.js                       100%  181KB   8.4MB/s   00:00    
index.data                     100%  140KB   6.4MB/s   00:00    

which can be experienced at http://varia.artificiel.org/of/imageSubsectionExample

[ofTheo]

Thanks @artificiel 👍