Add some emacs/readline keybindings

[waf]

Add support for additional emacs / readline style keybindings.

Fixes #277

[codecov]

Codecov Report

❌ Patch coverage is 91.42857% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.5%. Comparing base (652df4e) to head (3781cb5).

Files with missing lines	Patch %	Lines
src/PrettyPrompt/Panes/CodePane.cs	90.7%	0 Missing and 5 partials ⚠️
src/PrettyPrompt/Panes/CompletionPane.cs	92.8%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #288   +/-   ##
=====================================
  Coverage   84.4%   84.5%           
=====================================
  Files         47      47           
  Lines       3931    3947   +16     
  Branches     654     655    +1     
=====================================
+ Hits        3321    3338   +17     
+ Misses       455     452    -3     
- Partials     155     157    +2     

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