upgrading to Bazel 7

- `.bazelrc`: `sandbox_add_mount_pair=/tmp/zig-cache` (if you can) or
  `/tmp` (if not) is now required everywhere.
- `.bazelrc` and `README`: remove deprecated/now-default flags.
- `README`: add links to #10 and #83.
- `README`: mention bzlmod.
- `examples/*/.bazelrc`: make them the same for a better recommendation.

Fixes #134.

.bazelrc

@@ -1,12 +1,9 @@
-common --enable_bzlmod
-
 test --sandbox_default_allow_network=false
 test --test_output=errors
 
 build --verbose_failures
 build --worker_sandboxing
 
-build --experimental_reuse_sandbox_directories
-build --incompatible_enable_cc_toolchain_resolution
 build --action_env BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1
 build --experimental_output_directory_naming_scheme=diff_against_dynamic_baseline
+build --sandbox_add_mount_pair=/tmp

.bazelversion

@@ -1 +1 @@
-6.4.0
+7.0.0