Add cpp-linter action

This uses the same .clang-format as numpy for consistency.

Author: Mousius

.clang-format

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+# A clang-format style that approximates Python's PEP 7
+# Useful for IDE integration
+#
+# Based on Paul Ganssle's version at
+# https://gist.github.com/pganssle/0e3a5f828b4d07d79447f6ced8e7e4db
+# and modified for NumPy
+BasedOnStyle: Google
+AlignAfterOpenBracket: Align
+AllowShortEnumsOnASingleLine: false
+AllowShortIfStatementsOnASingleLine: false
+AlwaysBreakAfterReturnType: TopLevel
+BreakBeforeBraces: Stroustrup
+ColumnLimit: 88
+ContinuationIndentWidth: 8
+DerivePointerAlignment: false
+IndentWidth: 4
+IncludeBlocks: Regroup
+IncludeCategories:
+  - Regex:           '^[<"](Python|structmember|pymem)\.h'
+    Priority:        -3
+    CaseSensitive:   true
+  - Regex:           '^"numpy/'
+    Priority:        -2
+  - Regex:           '^"(npy_pycompat|npy_config)'
+    Priority:        -1
+  - Regex:           '^"[[:alnum:]_.]+"'
+    Priority:        1
+  - Regex:           '^<[[:alnum:]_.]+"'
+    Priority:        2
+Language: Cpp
+PointerAlignment: Right
+ReflowComments: true
+SpaceBeforeParens: ControlStatements
+SpacesInParentheses: false
+StatementMacros: [PyObject_HEAD, PyObject_VAR_HEAD, PyObject_HEAD_EXTRA]
+TabWidth: 4
+UseTab: Never

.github/workflows/cpp-linter.yml

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+name: cpp-linter
+
+on:
+  pull_request:
+    branches:
+      - main
+    paths:
+      - "npsr/*"
+
+jobs:
+  cpp-linter:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+      - uses: cpp-linter/cpp-linter-action@f91c446a32ae3eb9f98fef8c9ed4c7cb613a4f8a
+        id: linter
+        continue-on-error: true
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          style: "file"
+
+      - name: Linter Outputs
+        if: steps.linter.outputs.checks-failed != 0
+        run: exit 1