History controller fix

[yescorp]

• Resolves #132

Also changes history controller behavior:

• Doesn't add initial record
• Adds record on any change if stack is empty
• NewLine adds record both before and after

[codecov[bot]]

Codecov Report

Merging #183 (a619a5c) into main (e2b10a5) will increase coverage by 0.05%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #183      +/-   ##
==========================================
+ Coverage   82.21%   82.26%   +0.05%     
==========================================
  Files          85       85              
  Lines        2552     2560       +8     
==========================================
+ Hits         2098     2106       +8     
  Misses        454      454              

Impacted Files	Coverage Δ
lib/src/code_field/code_controller.dart	79.62% <100.00%> (+0.06%)	:arrow_up:
lib/src/history/code_history_controller.dart	100.00% <100.00%> (ø)

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[yescorp]

Closing this PR because it is easier to create another branch