Introduce bump_version.yml to bump version when a PR is merged into master

[lewisblake]

Designed to close #969

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 79.27%. Comparing base (8a5d7e2) to head (1ea11e3). Report is 1843 commits behind head on main-dev.

Additional details and impacted files

@@            Coverage Diff            @@
##           main-dev     #986   +/-   ##
=========================================
  Coverage     79.26%   79.27%           
=========================================
  Files           109      109           
  Lines         19029    19031    +2     
=========================================
+ Hits          15084    15086    +2     
  Misses         3945     3945           

Flag	Coverage Δ
unittests	79.27% <ø> (+<0.01%)	:arrow_up:

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[lewisblake]

We deploy from main-dev so closing for now