add: fourmolu config

fourmolu.yaml

@@ -1,14 +1,51 @@
+# Number of spaces per indentation step
 indentation: 2
+
+# Max line length for automatic line breaking
+column-limit: none
+
+# Styling of arrows in type signatures (choices: trailing, leading, or leading-args)
 function-arrows: trailing
+
+# How to place commas in multi-line lists, records, etc. (choices: leading or trailing)
 comma-style: leading
+
+# Styling of import/export lists (choices: leading, trailing, or diff-friendly)
 import-export-style: diff-friendly
+
+# Whether to full-indent or half-indent 'where' bindings past the preceding body
 indent-wheres: false
+
+# Whether to leave a space before an opening record brace
 record-brace-space: false
+
+# Number of spaces between top-level declarations
 newlines-between-decls: 1
-haddock-style: multi-line
-haddock-style-module:
+
+# How to print Haddock comments (choices: single-line, multi-line, or multi-line-compact)
+haddock-style: single-line
+
+# How to print module docstring
+haddock-style-module: null
+
+# Styling of let blocks (choices: auto, inline, newline, or mixed)
 let-style: auto
+
+# How to align the 'in' keyword with respect to the 'let' keyword (choices: left-align, right-align, or no-space)
 in-style: right-align
+
+# Whether to put parentheses around a single constraint (choices: auto, always, or never)
+single-constraint-parens: always
+
+# Output Unicode syntax (choices: detect, always, or never)
+unicode: never
+
+# Give the programmer more choice on where to insert blank lines
 respectful: true
+
+# Fixity information for operators
 fixities: []
-unicode: never
+
+# Module reexports Fourmolu should know about
+reexports: []
+