flir 0.6.0

This release adds a few new features and fixes. flir is now presented as a
tool to refactor any type of code by detecting and rewriting custom patterns.

flir comes with a list of built-in rules and therefore can still be used as a linter,
but I now concentrate my efforts on a new R linter entirely written in Rust: Jarl.
Therefore, I will not add new rules in flir.

New features

• New linters:

  • expect_s3_class_linter() (@trevorld, #110)
  • expect_s4_class_linter() (@trevorld, #109)
  • nzchar_linter() (@trevorld, #102)
  • vector_logic_linter() (@trevorld, #111)

• New vignette "Tips and tricks" that lists some solutions for problems one may
  encounter when writing new rules (#94).

Bug fixes

• When using external rules with the with-<pkg> syntax, if the YAML file
  contains several rules separated by "---", then flir would only use the
  first one. This is now fixed (#95).

• list_linters() now uses path = "." by default (#99).

• lint_text() and fix_text() now work correctly with custom rules when the
  working directory is neither an R package nor an RStudio project (#119).

Changes

• expect_type_linter() now has less false positives for non-type is.*() functions
  and also provides more fixes (@trevorld, #110).