Add powder fitting tutorial

[RichardWaiteSTFC]

Have got a .html file generated but don't know if there are other steps required to publish it.

To-Do

• need to add test for bug fixed
• Some typos

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 42.65%. Comparing base (1b52407) to head (636a358).
Report is 15 commits behind head on master.

Files	Patch %	Lines
swfiles/sw_fitpowder.m	25.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #199      +/-   ##
==========================================
+ Coverage   42.37%   42.65%   +0.28%     
==========================================
  Files         240      241       +1     
  Lines       16184    16253      +69     
==========================================
+ Hits         6858     6933      +75     
+ Misses       9326     9320       -6     

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[github-actions]

Test Results

    4 files  ± 0    116 suites  +4   4m 56s ⏱️ +20s
  733 tests +13    715 ✅ +13  18 💤 ±0  0 ❌ ±0 
2 104 runs  +52  2 068 ✅ +52  36 💤 ±0  0 ❌ ±0 

Results for commit 636a358. ± Comparison against base commit 1b52407.

♻️ This comment has been updated with latest results.

[mducle]

Sorry I made a mistake in the instrument resolution parameters - could you change it and run publish_PSI('tutorial39.m') again please?

[mducle]

Looks good! Thanks