[feature] Add repository rule for translation of "properties" file into a .bzl

Context: https://github.com/bazelbuild/bazel/issues/18617; example: https://github.com/knik0/faad2/pull/162

Just asking if it is appropriate. If so, I'll prepare a PR.

Reasoning: normally to translate "properties" into skylark variables we have to

1. add repository rule into e.g. workspace.bzl
2. load and use that rule in WORKSPACE
3. load resulting .bzl in target BUILD file

Step (1) could be removed if such a rule is a part of `bazel-skylib`. As a stretch goal, we could add more input formats alongside nearly-native JSON.

Start by reviewing the linked Bazel issue and example pull request, then inspect how workspace.bzl, WORKSPACE, and the target BUILD file would participate in the proposed flow. Determine whether a bazel-skylib repository rule should translate properties files into .bzl variables, and define the supported input formats and expected generated output before implementing anything.

Written by the indexing model from the issue text.