ci, doc: Fix macOS runner, update README [ci skip]

Author: acgetchell

.github/workflows/macos.yml

@@ -16,6 +16,9 @@ jobs:
           fetch-depth: 0
           submodules: true
 
+      - name: Select Xcode 15.3 (Apple Clang 17)
+        run: sudo xcode-select -s /Applications/Xcode_15.3.app
+
       - name: Setup
         run: |
           declare -a python_files=("2to3", "idle3", "pydoc3", "python3", "python3-config")

README.md

@@ -66,7 +66,7 @@ Arbitrary-precision numbers and functions are by [MPFR] and [GMP].
 - [x] Develop using Behavior-driven development ([BDD]) with [doctest]
 - [x] Continuous integration by [Travis-CI] on macOS and Linux with [gcc]/[Clang]
 - [x] Continuous integration by [AppVeyor] on Windows with [MSVC]
-- [x] Continuous integration by [Github Actions] on the leading edge
+- [x] Continuous integration by [GitHub Actions] on the leading edge
 - [x] 3D Simplex
 - [x] 3D Spherical triangulation
 - [x] 2+1 foliation
@@ -260,7 +260,7 @@ Options:
 ~~~
 
 The dimensionality of the spacetime is such that each slice of spacetime is
-`d-1`-dimensional, so setting `d=3` generates 2 spacelike dimensions and one
+`d-1`-dimensional, so setting `d=3` generates two spacelike dimensions and one
 timelike dimension, with a defined global time foliation. A
 `d`-dimensional simplex will have some `d-1` sub-simplices that are purely
 spacelike (all on the same timeslice) as well as some that are timelike
@@ -281,7 +281,7 @@ doxygen ./docs/Doxyfile
 
 This will generate a `docs/html/` directory containing
 documentation generated from CDT++ source files. `USE_MATHJAX` has been enabled
-in [Doxyfile] so that the LaTeX formulae can be rendered in the html
+in [Doxyfile] so that the LaTeX formulae can be rendered in the HTML
 documentation using [MathJax]. `HAVE_DOT` is set to **YES** which allows
 various graphs to be autogenerated by [Doxygen] using [GraphViz].
 If you do not have GraphViz installed, set this option to **NO**
@@ -413,7 +413,10 @@ Optional:
 
 - [vcpkg]'s version of [date] has an unfixed bug [#23637] which produces `use-of-uninitialized-value` in [MemorySanitizer].
 - [vcpkg] has issues with `fontconfig:arm64-osx` [#40623].
+- [vcpkg] fails to build [gmp] on Linux (which breaks CI) [#45336]
 
+
+[#45336]: https://github.com/microsoft/vcpkg/issues/45336
 [#40623]: https://github.com/microsoft/vcpkg/issues/40623
 [#23637]: https://github.com/microsoft/vcpkg/issues/23637
 [CDT]: https://arxiv.org/abs/hep-th/0105267
@@ -480,7 +483,7 @@ Optional:
 [3]: https://github.com/microsoft/vcpkg/issues/8627
 [CONTRIBUTING.md]: https://github.com/acgetchell/CDT-plusplus/blob/develop/.github/CONTRIBUTING.md
 [CODE_OF_CONDUCT.md]: https://github.com/acgetchell/CDT-plusplus/blob/develop/.github/CODE_OF_CONDUCT.md
-[Github Actions]: https://github.com/features/actions
+[GitHub Actions]: https://github.com/features/actions
 [Visual Studio 2019]: https://visualstudio.microsoft.com/vs/
 [{fmt}]: https://github.com/fmtlib/fmt
 [AddressSanitizer]: https://github.com/google/sanitizers/wiki/AddressSanitizer