Add rule to remove if expressions

[jeparlefrancais]

Closes #208 Closes #207

This PR add a new rule that remove if expressions and convert them into an equivalent expression.

• add entry to the changelog
• update docs

[github-actions]

Coverage after merging remove-if-expression into main will be

87.02%

Coverage Report for Changed Files

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src/process/evaluator
mod.rs	87.74%	100%	98.18%	86.49%	102–103, 164, 176, 187, 198, 207–209, 215–217, 219–221, 223–224, 227, 239–241, 253–257, 261–262, 264–266, 306, 327, 341, 365, 368, 401, 407–408, 413, 427, 430, 448, 551, 58–60, 71, 812, 88–89
src/rules
mod.rs	89.03%	100%	82.86%	89.79%	114–116, 130–132, 150–152, 154, 185–187, 282, 322–324, 351, 358–361, 375, 424–426
remove_if_expression.rs	100%	100%	100%	100%