Rebase develop (#86)

* version bump to 0.2.0

* prepare the new crate notan_audio

* updated notan_math dependencies

* updated dependencies

* updated notan_winit to latest dependencies

* added wasm as category

* added support to open external links on web browsers

* changed set_config by add_config

* added support for drag&drop files using the winit backend

* hide the drop_files feature behind a feature flag

* wip new web to show examples

* added a script to help getting the example screenshots

* minor improvement

* fix build script

* wip: egui updated from 0.15 to 0.17

* minor change

* improved egui integration

* added support for premultiplied alpha

* fixed how the native textures are rendered on egui

* added UInt8 vertex formats. Renamed VertexFormat types with more descriptives names

* added support for srgba textures

* enable all-features for docs

* fixed gamma issues

* improve code readability and error handling

* added some sugar to the egui API

* cargo.lock updated

* adapted egui examples to the new sugar API

* added support to open links on new tabs

* hide the drop_files feature behind a feature flag

* added clipboard feature flag

* fix clipboard flag issue

* added drag&drop support for egui on native platforms

* drop files improvements

* drop files fixes

* added mime types

* minor fix

* removed mobile shader compilation for now

* fixed example issues

* removed unused image extensions

* lint fixes

* fixed #78

* removed core dependencie??

* added a lazy rendering mode using winit

* added a method to request the next frame in lazy mode

* minor improvements for the lazy mode

* lazy mode on web builds

* fixed lazy mode on web backend

* fix wasm issue where the lazy mode never request a new frame

* keyboard or mouse down will ask for a next frame

* support for mouse cursors using winit

* added custom cursor support on web

* enabled png and jpeg images only

* added lines primitives

* embraced glam.rs, all the types are now rexported from notan::math

* added an example about how to clear the screen

* minor fixes

* clippy fixes

* fixed example template

* added notan_audio to the crates list

* force egui to repaint after a window resize

* version 0.2.1

* cargo.lock updated