Re-added bazel support (#430)

BUILD.bazel

@@ -0,0 +1,15 @@
+_msvc_copts = ["/std:c++17"]	
+_gcc_copts = ["-std=c++17"]
+
+cc_library(
+    name = "entt",
+    visibility = ["//visibility:public"],
+    strip_include_prefix = "src",
+    hdrs = glob(["src/**/*.h", "src/**/*.hpp"]),
+    copts = select({
+      "@bazel_tools//src/conditions:windows": _msvc_copts,
+      "@bazel_tools//src/conditions:windows_msvc": _msvc_copts,
+      "@bazel_tools//src/conditions:windows_msys": _msvc_copts,
+      "//conditions:default": _gcc_copts,
+    }),
+)

README.md

@@ -222,6 +222,11 @@ documentation:
 * `CMake` version 3.7 or later.
 * `Doxygen` version 1.8 or later.
 
+Alternatively, [Bazel](https://bazel.build) is also supported as a build system
+(credits to [zaucy](https://github.com/zaucy) who offered to maintain it).<br/>
+In the documentation below I'll still refer to `CMake`, this being the official
+build system of the library.
+
 If you are looking for a C++14 version of `EnTT`, check out the git tag `cpp14`.
 
 ## Library

WORKSPACE

@@ -0,0 +1 @@
+workspace(name = "com_github_skypjack_entt")