Rewrite Query Language docs

[ddelemeny]

Piggybacking on @trinity-1686a's update proposal for the query language documentation in #4708.

I extracted and formatted a "friendly" version to be included in the Getting started section of the docs and rewrote the refdoc in a more formal way

• Extract an introduction to the query language
• Rewrite the QL reference doc in a more systematic and exhaustive way.

Quickwit.io screenshots

Intro

Reference

[ddelemeny]

Okay, that should to the trick. Please make sure I didn't leave obvious mistakes in my interpretation.

@trinity-1686a I've left a few comments in the refdoc where I think some clarification is needed, feel free to chime in !

Edit: information is also missing about the single quote syntax for terms used by @fmassot in quickwit-oss/quickwit-datasource#102

[trinity-1686a]

I don't think we have a name for field:'my value' queries. It's a bit like a phrase query in the sense that it matches only if field contains both my and value; but it doesn't check positions (i.e. they can be distant or not in the right order). It's also a convenient way to query fields with the raw tokenizer when the value contain spaces (which can also be done with field:my\ value I believe)

[ddelemeny]

Thanks for the review @trinity-1686a!
@fmassot I think the docs are ready to merge.