String and List Methods

[kellrott]

This PR adds

• string.startswith
• string.endswith
• list.append
• list.extend

[codecov-io]

Codecov Report

Merging #61 into master will increase coverage by 0.06%.
The diff coverage is 81.13%.

@@            Coverage Diff             @@
##           master      #61      +/-   ##
==========================================
+ Coverage   68.38%   68.44%   +0.06%     
==========================================
  Files          59       59              
  Lines       10435    10488      +53     
==========================================
+ Hits         7136     7179      +43     
- Misses       2794     2803       +9     
- Partials      505      506       +1

Impacted Files	Coverage Δ
py/string.go	86.94% <79.48%> (-1.27%)	⬇️
py/list.go	30.05% <85.71%> (+4.61%)	⬆️

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[ncw]

That looks great thank you :-)

Will merge now.