add LinearAlgebra to deps

[ctarn]

Colors.jl use LinearAlgebra, but doesn't include it in deps.

It would cause an error when using PackageCompiler.jl. The error message is:

ERROR: LoadError: MethodError: no method matching inv(::Matrix{Float64})
The function `inv` exists, but no method is defined for this combination of argument types.

Closest candidates are:
  inv(::ComplexF64)
   @ Base complex.jl:479
  inv(::BigFloat)
   @ Base mpfr.jl:678
  inv(::Missing)
   @ Base missing.jl:101
  ...

Stacktrace:
 [1] top-level scope
   @ ~/.julia/packages/Colors/VFEJ1/src/conversions.jl:616
 [2] top-level scope
   @ ~/.julia/packages/Colors/VFEJ1/src/Colors.jl:30
 [3] top-level scope
   @ stdin:5

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.76%. Comparing base (6a62c64) to head (42d8570).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #576   +/-   ##
=======================================
  Coverage   98.76%   98.76%           
=======================================
  Files          10       10           
  Lines        1293     1293           
=======================================
  Hits         1277     1277           
  Misses         16       16           

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[kimikage]

Actually, since inv() is only used to generate constants, it should be possible to remove it.
However, I believe that depending on LinearAlgebra wouldn't cause any practical problems.

Thank you.