Rename useQueryString to readonly

[nezed]

Motivation:

• Provide easy way to turn query into readonly mode.
• useQueryString turns connection in readonly mode, which may be unexpected.
• { queryOptions: { readonly: true } } are ignored by CH, which may be unexpected.

[codecov-io]

Codecov Report

Merging #40 into master will increase coverage by 0.03%. The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #40      +/-   ##
=======================================
+ Coverage   87.96%   88%   +0.03%     
=======================================
  Files           6     6              
  Lines         324   325       +1     
=======================================
+ Hits          285   286       +1     
  Misses         39    39

Impacted Files	Coverage Δ
src/clickhouse.js	96.31% <100%> (+0.02%)	:arrow_up:

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