Add BlockDiagonalOperator and TimedLinearOperator in the documentation

[amontoison]

No description provided.

[coveralls]

Coverage remained the same at 96.332% when pulling 06d1956 on amontoison:docs into f56bda1 on JuliaSmoothOptimizers:master.

[codecov]

Codecov Report

Merging #149 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #149   +/-   ##
=======================================
  Coverage   96.33%   96.33%           
=======================================
  Files          14       14           
  Lines         627      627           
=======================================
  Hits          604      604           
  Misses         23       23           

Impacted Files	Coverage Δ
src/TimedOperators.jl	75.00% <ø> (ø)
src/special-operators.jl	86.20% <ø> (ø)

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[abelsiqueira]

Thanks