ENH: Add a frequency analysis template for CP2K

[BvB93]

This PR adds the qmflows.freq.cp2k template, which can be used for performing frequency analyses.
The template is effectively a hybrid of the pre-existing freq.cp2k_mm and singlepoint.cp2k templates.

[codecov]

Codecov Report

Merging #278 (ee3492c) into master (03a658c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #278   +/-   ##
=======================================
  Coverage   82.02%   82.02%           
=======================================
  Files          41       41           
  Lines        2131     2131           
  Branches      353      353           
=======================================
  Hits         1748     1748           
  Misses        299      299           
  Partials       84       84           

Impacted Files	Coverage Δ
src/qmflows/templates/templates.py	100.00% <ø> (ø)

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