client: Add tag autocomplete

[jtojnar]

Fixes: https://github.com/fossar/selfoss/issues/669

• [x] Show colours for tags when editing starts
• [x] Show colours in autocomplete
• [ ] Add copy button
• [x] Newly added tags lack colours https://github.com/i-like-robots/react-tags/pull/260
• [ ] Auto assign colours for newly created tags
• [ ] Allow changing tag colours
• [ ] handle tags with HTML special characters like “ham & eggs” or “<3” correctly
• [ ] Add support for new tag message suffix https://github.com/i-like-robots/react-tags/issues/262