Add detect-language CLI command

[osma]

This PR adds a detect-language CLI command, as specified in #799.

Here is how it works:

$ echo "this is example text" | annif detect-language fi,sv,en
en	1.0000
sv	0.3333
fi	0.0000
?	0.0000

This is slightly different than what was proposed in #799. The candidate languages are given as an argument (comma-delimited) instead of a --languages option, and the unknown language case is shown as ? not -.

It's also possible to run this on multiple files, just like annif suggest:

$ annif detect-language fi,sv,en README.md LICENSE.txt 
Detected languages for README.md
en	0.7700
sv	0.2100
?	0.2000
fi	0.1400
Detected languages for LICENSE.txt
en	0.8857
sv	0.3714
fi	0.0857
?	0.0571

Special cases / errors:

$ echo "this is example text" | annif detect-language xx yy
Usage: annif detect-language [OPTIONS] [LANGUAGES]...
Try 'annif detect-language --help' for help.

Error: Unsupported language: xx

$ annif detect-language
Usage: annif detect-language [OPTIONS] LANGUAGES [PATHS]...
Try 'annif detect-language --help' for help.

Error: Missing argument 'LANGUAGES'.

Closes #799

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.65%. Comparing base (c81ed1c) to head (0dda55b).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #801   +/-   ##
=======================================
  Coverage   99.65%   99.65%           
=======================================
  Files          93       93           
  Lines        6889     6939   +50     
=======================================
+ Hits         6865     6915   +50     
  Misses         24       24           

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud