Build, install, and check json_view.hpp

The new single header goes through the same checks and install steps as
json.hpp and json_fwd.hpp:

- cmake/ci.cmake: ci_test_amalgamation regenerates, formats, and compares
  json_view.hpp as well
- check_amalgamation.yml: the pull request check does the same; it runs
  develop's tools, so it needs config_json_view.json on develop first
- meson.build: installs single_include/nlohmann/json_view.hpp
- gen_bazel_build_file.cmake, BUILD.bazel: json_view.hpp joins the
  single-header target; the glob of the other target already covers the
  new headers
- labeler.yml: an "aspect: json_view" label for the header, its
  detail/view headers, tests, and documentation

The CMake install rules for include/ and single_include/, the REUSE
catch-all, and Package.swift cover the new files without changes.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

cmake/scripts/gen_bazel_build_file.cmake

@@ -48,6 +48,7 @@ cc_library(
     name = "singleheader-json",
     hdrs = [
         "single_include/nlohmann/json.hpp",
+        "single_include/nlohmann/json_view.hpp",
     ],
     includes = ["single_include"],
     visibility = ["//visibility:public"],