restructure into smaller files & add IWYU/clang-tidy

Signed-off-by: Folling <mail@folling.io>

.clang-format

@@ -81,72 +81,31 @@ FixNamespaceComments: false
 
 IncludeBlocks: Regroup
 IncludeCategories:
-  # Relative Includes
-  # "blubb.h" / "blubb/blubber.h"
   - Regex: '^".+\.(h|hpp)"$'
     Priority: 1
-
-  # C Includes
-  # <string.h>
   - Regex: '^<[a-z0-9_]+\.h>$'
     Priority: 2
-
-  # C++ Includes
-  # <string>
   - Regex: '^<[a-z0-9_]+>$'
     Priority: 3
-
-  # expected
-  # <expected/ranges.hpp>
   - Regex: '^<expected/.*>$'
     Priority: 4
-
-  # libfmt
-  # <fmt/core.hpp>
   - Regex: '^<fmt/.*>$'
     Priority: 5
-
-  # nlohmann::json
-  # <nlohmann/json.hpp>
   - Regex: '^<nlohmann/.*>$'
     Priority: 6
-
-  # ranges
-  # <range-v3/ranges.hpp>
   - Regex: '^<range-v3/.*>$'
     Priority: 7
-
-  # ICU
-  # <unicode/ranges.hpp>
-  - Regex: '^<unicode/.*>$'
+  - Regex: '^<catch2/.*>$'
     Priority: 8
-
-  # ranges
-  # <range-v3/ranges.hpp>
-  - Regex: '^<cppbase/.*>$'
+  - Regex: '^<unicode/.*>$'
     Priority: 9
-
-  # ranges
-  # <range-v3/ranges.hpp>
-  - Regex: '^<sqlitecpp/.*>$'
+  - Regex: '^<cppbase/.*>$'
     Priority: 10
-
-  # ranges
-  # <range-v3/ranges.hpp>
-  - Regex: '^<ikarus/.*>$'
+  - Regex: '^<sqlitecpp/.*>$'
     Priority: 11
-
-  # ranges
-  # <range-v3/ranges.hpp>
-  - Regex: '^<generated/.*>$'
+  - Regex: '^<ikarus/.*>$'
     Priority: 12
 
-  # ranges
-  # ranges
-  # <range-v3/ranges.hpp>
-  - Regex: '^<impl/.*>$'
-    Priority: 13
-
 IndentAccessModifiers: false
 IndentCaseBlocks: false
 IndentCaseLabels: false