loadSources(
        sources,
        texturesOptions,
        successCallback,
        errorCallback
    ) {
        for(let i = 0; i < sources.length; i++) {
            this.loadSource(sources[i], texturesOptions, successCallback, errorCallback);
        }
    }
This method loads an array of sources by calling loadSource() for each one of them

     params:
     @sources (array of html elements / sources url): array of html images, videos, canvases element or sources url
     @texturesOptions (object): parameters to apply to the textures, such as sampler name, repeat wrapping, filters, anisotropy...
     @successCallback (function): function to execute when each source has been loaded
     @errorCallback (function): function to execute if a source fails to load
*