Autocorrect typos during autocomplete

[evazion]

Typos should be automatically corrected during tag autocompletion. If your tag has a typo and no completions can be found, then autocomplete should list tags similar to what you typed. It's possible to do this easily and efficiently with a fuzzy string search using Postgres' builtin trigram operators.

I raised this idea in #3352. I think typos when adding tags could often be avoided if they were caught at the autocomplete stage. Not to mention how useful autocorrect would be for searches in general.

Refs:

• http://tapoueh.org/blog/2013/09/using-trigrams-against-typos/
• https://www.postgresql.org/docs/current/static/pgtrgm.html#idm46428634524336
• https://www.postgresql.org/docs/10/static/fuzzystrmatch.html#idm46428636025488