Add a bazel rule for generating erlang_ls.config

If you are using bazel, you can switch to this with:
1. `bazelisk build //tools:erlang_ls.config`
2. `cp bazel-bin/tools/erlang_ls.config erlang_ls.config`

tools/BUILD.bazel

@@ -0,0 +1,5 @@
+load(":erlang_ls.bzl", "erlang_ls_config")
+
+erlang_ls_config(
+    name = "erlang_ls.config",
+)

tools/erlang_ls.bzl

@@ -0,0 +1,35 @@
+load("@bazel-erlang//:erlang_home.bzl", "ErlangHomeProvider")
+
+def _impl(ctx):
+    out = ctx.actions.declare_file(ctx.label.name)
+
+    erlang_home = ctx.attr._erlang_home[ErlangHomeProvider].path
+
+    ctx.actions.write(
+        output = out,
+        content = """otp_path: {erlang_home}
+apps_dirs:
+  - deps/*
+deps_dirs:
+  - bazel-bin/external/*
+include_dirs:
+  - deps
+  - deps/*/include
+  - bazel-bin/external
+  - bazel-bin/external/*/include
+plt_path: bazel-bin/deps/rabbit/.base_plt.plt
+""".format(
+            erlang_home = erlang_home,
+        ),
+    )
+
+    return [
+        DefaultInfo(files = depset([out])),
+    ]
+
+erlang_ls_config = rule(
+    implementation = _impl,
+    attrs = {
+        "_erlang_home": attr.label(default = "@bazel-erlang//:erlang_home"),
+    },
+)