[MRG] provide minimum sourmash version information about sketch fromfile

[ctb]

Fixes #2007.

Also squashes toctree warnings during doc build.

@mr-eyes should be ready for review!

[codecov]

Codecov Report

Merging #2009 (d7a93d6) into latest (14f3d7a) will increase coverage by 7.52%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           latest    #2009      +/-   ##
==========================================
+ Coverage   84.14%   91.66%   +7.52%     
==========================================
  Files         129       98      -31     
  Lines       15082    10802    -4280     
  Branches     2118     2118              
==========================================
- Hits        12691     9902    -2789     
+ Misses       2095      604    -1491     
  Partials      296      296              

Flag	Coverage Δ
python	91.66% <ø> (ø)
rust	?

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Impacted Files	Coverage Δ
src/core/src/sketch/hyperloglog/mod.rs
src/core/src/ffi/minhash.rs
src/core/src/index/linear.rs
src/core/src/from.rs
src/core/src/storage.rs
src/core/src/errors.rs
src/core/src/cmd.rs
src/core/src/sketch/minhash.rs
src/core/src/encodings.rs
src/core/src/index/sbt/mod.rs
... and 21 more

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[ctb]

@sourmash-bio/devs ready for review and (maybe) merge! this is a nice easy one! get your reviewing credits in here!

[mr-eyes]

LGTM!