[WIP] Add Web support

[Fintasys]

This PR adds Web to the list of supported Platforms.

Issue: #2

Open Issues:

• When using custom fonts, Emoji's are not correctly displayed in their text fields when selected. Solution would be custom RichTextInput like explained here https://stackoverflow.com/questions/44936239/displaying-text-with-emojis-on-flutter
• (low priority) custom font doesn't work in android/ios, probably emoji needs to be rendered at the start of the app in order to trigger loading the custom font.

[caleb654]

Web support would be so awesome!

[moonjoungyoung]

@Fintasys

This will be very good. flutter web needs emoji.

Is it able to use this PR for beta ..?

[dna-f]

Hi! any news on this PR?

[LostInDarkMath]

Hey @Fintasys any news on this?

[hatemragab]

i have tried it not working on the web

[Fintasys]

Closing in favor for https://github.com/Fintasys/emoji_picker_flutter/pull/103