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.