Support RxDB 10

[cvara]

• Support (and test against) the latest version of rxdb (10.3.0 as of the time of writing)
• Include compatibility table in readme to dispel confusion

[codecov]

Codecov Report

Merging #39 (9cdc226) into master (e2db976) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #39   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            7         7           
  Lines          134       135    +1     
  Branches        28        28           
=========================================
+ Hits           134       135    +1     

Impacted Files	Coverage Δ
src/useRxDocument.ts	100.00% <ø> (ø)
src/plugins.ts	100.00% <100.00%> (ø)
src/useRxQuery.ts	100.00% <100.00%> (ø)

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