Add size(::RQPackedQ)

[dkarrasch]

I somehow overlooked that in my previous PR. Interestingly, RQPackedQ is not subtyping LayoutQ, so it's not affected by the generic size method.

[codecov]

Codecov Report

Merging #32 (5047e20) into master (02e6b7b) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #32   +/-   ##
=======================================
  Coverage   93.01%   93.02%           
=======================================
  Files           7        7           
  Lines        1045     1046    +1     
=======================================
+ Hits          972      973    +1     
  Misses         73       73           

Impacted Files	Coverage Δ
src/rq.jl	94.67% <100.00%> (+0.02%)	⬆️

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[dlfivefifty]

The fact that RQPackedQ is not <: LayoutQ is probably an oversight but we can leave that for now. LayoutQ is only really useful for ∞-dimensional factorisations as implemented in InfiniteLinearAlgebra.jl.