clang-format: Add file

Related: apps/orage#32, xfce4-dev-tools!101

.clang-format

+---
+Language: Cpp
+BasedOnStyle: LLVM
+
+AlignEscapedNewlines: DontAlign
+AlignTrailingComments: Never
+AllowAllParametersOfDeclarationOnNextLine: false
+AlwaysBreakAfterDefinitionReturnType: All
+AlwaysBreakAfterReturnType: All
+BinPackParameters: false
+BreakBeforeBinaryOperators: All
+BreakBeforeBraces: Allman
+ColumnLimit: 0
+ContinuationIndentWidth: 2
+Cpp11BracedListStyle: false
+IndentCaseLabels: true
+IndentGotoLabels: false
+InsertNewlineAtEOF: true
+KeepEmptyLinesAtTheStartOfBlocks: false
+MaxEmptyLinesToKeep: 3
+SpaceAfterCStyleCast: true
+SpaceBeforeParens: Always
+# Buggy workaround to add exceptions to 'SpaceBeforeParens: Always' (see below)
+WhitespaceSensitiveMacros:
+  - _
+# Workaround to avoid some alignment bugs when adding a macro to WhitespaceSensitiveMacros,
+# see https://github.com/llvm/llvm-project/issues/55443#issuecomment-1953268337
+# This doesn't fix all alignment bugs though, so I'd rather make an exception only for '_',
+# and not also for 'N_' or 'I_' for example.
+# See also https://github.com/llvm/llvm-project/issues/82288
+Macros:
+  - _(x)=x
+...