Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/libwebp/versions.

These checks were done:

- built on NixOS
- ran ‘/nix/store/7rlf92q1g4sxv0g1gj8sf8310zm9na88-libwebp-1.0.0/bin/dwebp -h’ got 0 exit code
- ran ‘/nix/store/7rlf92q1g4sxv0g1gj8sf8310zm9na88-libwebp-1.0.0/bin/cwebp -h’ got 0 exit code
- ran ‘/nix/store/7rlf92q1g4sxv0g1gj8sf8310zm9na88-libwebp-1.0.0/bin/gif2webp -h’ got 0 exit code
- ran ‘/nix/store/7rlf92q1g4sxv0g1gj8sf8310zm9na88-libwebp-1.0.0/bin/img2webp -h’ got 0 exit code
- ran ‘/nix/store/7rlf92q1g4sxv0g1gj8sf8310zm9na88-libwebp-1.0.0/bin/img2webp --help’ got 0 exit code
- ran ‘/nix/store/7rlf92q1g4sxv0g1gj8sf8310zm9na88-libwebp-1.0.0/bin/webpmux -h’ got 0 exit code
- ran ‘/nix/store/7rlf92q1g4sxv0g1gj8sf8310zm9na88-libwebp-1.0.0/bin/webpinfo -h’ got 0 exit code
- found 1.0.0 with grep in /nix/store/7rlf92q1g4sxv0g1gj8sf8310zm9na88-libwebp-1.0.0
- directory tree listing: https://gist.github.com/a09e2cd5f3d318ac588ecdf308cc9898

libwebp: 0.6.1 -> 1.0.0