add edge-ngram elastic search example

[equivalent]

example of https://www.elastic.co/guide/en/elasticsearch/reference/current/analysis-edgengram-tokenizer.html

this is supper helpful to understand not only edge-ngrams, but how to actually define own analysis with elasticsearch-rails

[equivalent]

tests are failing due to Make sure thatgem install mime-types-data -v '3.2016.0521'succeeds before nothing to do with the code change,

[equivalent]

@karmi any feedback on this PR ?

[karmi]

Hi Tomas, apologies for this ridiculous delay; I haven't been able to find time to process patches and respond to questions in this repository for a long time.

I've re-worded the commit message a bit, and I've translated the analysis output you had in comments into code, using the "Indices Analyze" API, in hope that it will add some didactic value to people.

When I was considering the example just now, I was wondering if we should have exactly this as an example for "home-grown" autocomplete -- people should use the dedicated Completion Suggester for that if at all possible; there's a Ruby example in activerecord_mapping_completion.rb.

However, I think the example still has value, and it's actually good that it is feature-wise very similar to the "completion" example. I'm thinking about actually expanding it a little bit, maybe by adding a different ngram filter, which would allow "infix" (inside-the-words) searches.

[equivalent]

Hi Karmi, no worries.

Yeah it's up to you really I've got this piece of code in my Gist so people can still find it if they need :)
So feel free to change it / close it/ rewrite it. During the time I was writing this for my employer I struggled to find similar example so had to come up with own one. So thought it would be helpful to have it here + it it's a good way to get feedback by a Pro on this topic.

čus

[karmi]

@equivalent, the patch has been merged in f8df53a :) Thanks again!

[equivalent]

@karmi awesome !! :) thank you