Allow emoji characters in text fields

[jannisborgers]

At the moment, SEOmatic fields like the site meta description cannot have emoji characters. If you put them in (via pasting or via the native macOS HUD), the whole field gets emptied when you save your changes.

Also discussed with nystudio107 and CraftCMS on Twitter:
https://twitter.com/CraftCMS/status/954276944228634624

Possible solution posted by CraftCMS:

We just added support for emojis in Plain Text fields in this week’s update, by swapping them with :shortcodes: on save (and back to unicode on retrieval).

Steps to reproduce:

• Open Site Meta
• Put text into Site SEO description
• Paste an emoji
• Save changes

Expected behavior:

• Emoji gets output in the template
• Full text including emoji is saved in Craft database

Actual behavior:

• Content of text field gets emptied
• No text is displayed in the template