.clang-format to report at [[clang-format] Improve clang-formats handling of concepts](https://reviews.llvm.org/D79773).

.clang-format

# Clang 11
AccessModifierOffset: -4
AlignAfterOpenBracket: AlwaysBreak
AlignConsecutiveAssignments: true
AlignConsecutiveBitFields: true
AlignConsecutiveDeclarations: false
AlignEscapedNewlines: Right
AlignOperands: Align
AlignTrailingComments: true
AllowAllArgumentsOnNextLine: true
AllowAllConstructorInitializersOnNextLine: true
AllowAllParametersOfDeclarationOnNextLine: true
AllowShortBlocksOnASingleLine: Never
AllowShortCaseLabelsOnASingleLine: false
AllowShortEnumsOnASingleLine: false
AllowShortFunctionsOnASingleLine: None
AllowShortIfStatementsOnASingleLine: Never
AllowShortLambdasOnASingleLine: All
AllowShortLoopsOnASingleLine: false
AlwaysBreakAfterReturnType: None
AlwaysBreakBeforeConceptDeclarations: true
AlwaysBreakBeforeMultilineStrings: true
AlwaysBreakTemplateDeclarations: Yes
BinPackArguments: true
BinPackParameters: true
BreakBeforeBinaryOperators: None
BreakBeforeBraces: Allman
BreakBeforeTernaryOperators: true
BreakConstructorInitializers: BeforeColon
BreakInheritanceList: BeforeColon
BreakStringLiterals: true
ColumnLimit: 80
ConstructorInitializerAllOnOneLineOrOnePerLine: true
ConstructorInitializerIndentWidth: 2
ContinuationIndentWidth: 4
Cpp11BracedListStyle: true
DeriveLineEnding: false
DerivePointerAlignment: false
DisableFormat: false
FixNamespaceComments: true
IncludeBlocks: Merge
IncludeCategories:
    -   Regex:      '<[a-z_]+>' # C++ standard library
        Priority:   1
IndentCaseBlocks: false
IndentCaseLabels: false
IndentPPDirectives: AfterHash
IndentRequires: true
IndentWidth: 4
IndentWrappedFunctionNames: false
KeepEmptyLinesAtTheStartOfBlocks: false
Language: Cpp
MaxEmptyLinesToKeep: 1
NamespaceIndentation: Inner
#PenaltyReturnTypeOnItsOwnLine: 9000
PointerAlignment: Left
ReflowComments: true
SortIncludes: true
SpaceAfterLogicalNot: false
SpaceAfterTemplateKeyword: true
SpaceBeforeAssignmentOperators: true
SpaceBeforeCpp11BracedList: false
SpaceBeforeCtorInitializerColon: true
SpaceBeforeInheritanceColon: true
SpaceBeforeRangeBasedForLoopColon: true
SpaceBeforeSquareBrackets: false
SpacesInConditionalStatement: false
SpaceInEmptyBlock: true
SpaceInEmptyParentheses: false
SpacesBeforeTrailingComments: 1
SpacesInAngles: false
SpacesInParentheses: false
SpacesInSquareBrackets: false
Standard: c++20
TabWidth: 4
UseCRLF: false
UseTab: Never