Add methodology documentation

[spahrenk]

Description

• The ppt presentation was transcribed to an md with minor changes .
• A null_implementation_test was added.

Author Progress Checklist:

• [x] Open draft pull request
  • [x] Make title clearly understandable in a standalone change log context
  • [x] Assign yourself the issue
  • [x] Add at least one label (enhancement, bug, or maintenance)
  • [x] Link the issue(s) addressed by this PR (under "Development" in the sidebar menu)
• [x] Make code changes (if you haven't already)
• [x] Self-review of code
  • [x] My code follows the style guidelines of this project
  • [x] I have added comments to my code, particularly in hard-to-understand areas
  • [x] I have only committed the necessary changes for this fix or feature
  • [x] I have made corresponding changes to the documentation
  • [x] My changes generate no new warnings
  • [x] I have ensured that my fix is effective or that my feature works as intended by:
    • [x] exercising the code changes in the test framework, and/or
    • [x] manually verifying the changes (as explained in the the pull request description above)
  • [x] My changes pass all local tests
  • [x] My changes successfully passes CI checks
  • [x] Add any unit test for proof and documentation.
  • [ ] Merge in main branch and address resulting conflicts and/or test failures.
• [ ] Move pull request out of draft mode and assign reviewers
• [ ] Iterate with reviewers until all changes are approved
  • [ ] Make changes in response to reviewer comments
  • [ ] Merge in main branch and address resulting conflicts and/or test failures.
  • [ ] Re-request review in GitHub

Reviewer Checklist:

• [ ] Read the pull request description
• [ ] Perform a code review on GitHub
• [ ] Confirm all CI checks pass and there are no build warnings
• [ ] Pull, build, and run automated tests locally
• [ ] Perform manual tests of the fix or feature locally
• [ ] Add any review comments, if applicable
• [ ] Submit review in GitHub as either
  • [ ] Request changes, or
  • [ ] Approve
• [ ] Iterate with author until all changes are approved

[codecov-commenter]

Codecov Report

Merging #32 (07cffb7) into main (9bab8ed) will increase coverage by 3.40%. Report is 51 commits behind head on main. The diff coverage is 85.93%.

@@            Coverage Diff             @@
##             main      #32      +/-   ##
==========================================
+ Coverage   82.56%   85.96%   +3.40%     
==========================================
  Files           5        6       +1     
  Lines         453      520      +67     
==========================================
+ Hits          374      447      +73     
+ Misses         79       73       -6     

Flag	Coverage Δ
integration	85.96% <85.93%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
include/btwxt/grid-axis.h	0.00% <0.00%> (ø)
include/btwxt/grid-point-data.h	0.00% <0.00%> (ø)
include/btwxt/logging.h	0.00% <0.00%> (ø)
src/regular-grid-interpolator-implementation.h	13.79% <13.79%> (ø)
src/grid-axis.cpp	85.33% <85.33%> (-8.00%)	:arrow_down:
src/regular-grid-interpolator.cpp	92.67% <92.65%> (+5.93%)	:arrow_up:

[spahrenk]

Curve colors had been reversed in the most recent commit. An attempt was made to correct this.

[spahrenk]

Replaced actual slopes with estimated slope son cubic figure.