Implemented "+" and "-" operators

[ascandone]

NOTE: auto-merge is on

PR can be looked at commit by commit

"+" and "-" specs:

• is defined for numbers (including negative numbers)
• is defined for monetaries of the same asset
• left and right operand need to have the same type, there is currently no form of implicit casting

[codecov]

Codecov Report

Attention: Patch coverage is 79.82196% with 204 lines in your changes missing coverage. Please review.

Project coverage is 63.33%. Comparing base (f6d4e75) to head (b959dc3).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/parser/antlr/numscript_parser.go	72.89%	137 Missing and 8 partials ⚠️
internal/interpreter/evaluate_expr.go	82.75%	12 Missing and 3 partials ⚠️
internal/interpreter/infix.go	67.39%	11 Missing and 4 partials ⚠️
internal/parser/ast.go	0.00%	9 Missing ⚠️
internal/parser/antlr/numscript_base_listener.go	0.00%	8 Missing ⚠️
internal/interpreter/value.go	87.23%	4 Missing and 2 partials ⚠️
internal/analysis/hover.go	85.18%	3 Missing and 1 partial ⚠️
internal/analysis/check.go	96.66%	1 Missing ⚠️
internal/parser/parser.go	97.56%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #25      +/-   ##
==========================================
+ Coverage   63.27%   63.33%   +0.05%     
==========================================
  Files          28       29       +1     
  Lines        6217     6395     +178     
==========================================
+ Hits         3934     4050     +116     
- Misses       2115     2167      +52     
- Partials      168      178      +10     

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