Index JSON by system, and sort/dedup outPaths

[srid]

Resolves #39

Also makes JSON the only & default flake output.

With 1 system

// jq < $(nix build --no-link --print-out-paths . --override-input flake github:srid/emanote)
{
  "x86_64-linux": {
    "byName": {
      "emanote": "/nix/store/3c17109qkg25py0h39909zac89aqwbvp-emanote-1.5.2.1",
      "emanote-dev": "/nix/store/2hsvz5kwxm6k4aw44i9lb065ihdvdp7b-emanote-dev",
      "emanote-docs-linkCheck": "/nix/store/md0y23sc68gq5j4br7ag7a3j8bgg1k02-emanote-docs-linkCheck",
      "emanote-static-website-docs": "/nix/store/0bvav8vc2xsshbxy564jfvwplvnpcvkb-emanote-static-website-docs",
      "pre-commit-run": "/nix/store/cdbfy4j0cl2lbn5a72kzh8hl1h0crw00-pre-commit-run"
    },
    "outPaths": [
      "/nix/store/0bvav8vc2xsshbxy564jfvwplvnpcvkb-emanote-static-website-docs",
      "/nix/store/2hsvz5kwxm6k4aw44i9lb065ihdvdp7b-emanote-dev",
      "/nix/store/3c17109qkg25py0h39909zac89aqwbvp-emanote-1.5.2.1",
      "/nix/store/3c17109qkg25py0h39909zac89aqwbvp-emanote-1.5.2.1/bin/emanote",
      "/nix/store/cdbfy4j0cl2lbn5a72kzh8hl1h0crw00-pre-commit-run",
      "/nix/store/md0y23sc68gq5j4br7ag7a3j8bgg1k02-emanote-docs-linkCheck",
      "/nix/store/ndxvfzirwzx2kg7vfp57r3n29r5ddixy-emanote-with-layers-docs/bin/emanote-with-layers-docs"
    ]
  }
}

With 2 systems

// jq < $(nix build --no-link --print-out-paths . --override-input flake github:srid/emanote --override-input systems github:srid/nix-systems?dir=aarch64-darwin,x86_64-linux)
{
  "aarch64-darwin": {
    "byName": {
      "emanote": "/nix/store/kr18g91xq7d103byp6f4ja5d9j5mil3a-emanote-1.5.2.1",
      "emanote-dev": "/nix/store/kn35hsdaim8m6s6njnghxr5y4yfaqm2y-emanote-dev",
      "emanote-docs-linkCheck": "/nix/store/y5wah3f0jm6nkiqdgdqd1i9m6k451f7q-emanote-docs-linkCheck",
      "emanote-static-website-docs": "/nix/store/wjnvwdmam8xl126n2slrii15c9j99c5v-emanote-static-website-docs",
      "pre-commit-run": "/nix/store/nhn2fy1s5sc5k7qhv75xqz31s26221bw-pre-commit-run"
    },
    "outPaths": [
      "/nix/store/gar8zbz2njwzzvai2iqvny55xckcfrfv-emanote-with-layers-docs/bin/emanote-with-layers-docs",
      "/nix/store/kn35hsdaim8m6s6njnghxr5y4yfaqm2y-emanote-dev",
      "/nix/store/kr18g91xq7d103byp6f4ja5d9j5mil3a-emanote-1.5.2.1",
      "/nix/store/kr18g91xq7d103byp6f4ja5d9j5mil3a-emanote-1.5.2.1/bin/emanote",
      "/nix/store/nhn2fy1s5sc5k7qhv75xqz31s26221bw-pre-commit-run",
      "/nix/store/wjnvwdmam8xl126n2slrii15c9j99c5v-emanote-static-website-docs",
      "/nix/store/y5wah3f0jm6nkiqdgdqd1i9m6k451f7q-emanote-docs-linkCheck"
    ]
  },
  "x86_64-linux": {
    "byName": {
      "emanote": "/nix/store/3c17109qkg25py0h39909zac89aqwbvp-emanote-1.5.2.1",
      "emanote-dev": "/nix/store/2hsvz5kwxm6k4aw44i9lb065ihdvdp7b-emanote-dev",
      "emanote-docs-linkCheck": "/nix/store/md0y23sc68gq5j4br7ag7a3j8bgg1k02-emanote-docs-linkCheck",
      "emanote-static-website-docs": "/nix/store/0bvav8vc2xsshbxy564jfvwplvnpcvkb-emanote-static-website-docs",
      "pre-commit-run": "/nix/store/cdbfy4j0cl2lbn5a72kzh8hl1h0crw00-pre-commit-run"
    },
    "outPaths": [
      "/nix/store/0bvav8vc2xsshbxy564jfvwplvnpcvkb-emanote-static-website-docs",
      "/nix/store/2hsvz5kwxm6k4aw44i9lb065ihdvdp7b-emanote-dev",
      "/nix/store/3c17109qkg25py0h39909zac89aqwbvp-emanote-1.5.2.1",
      "/nix/store/3c17109qkg25py0h39909zac89aqwbvp-emanote-1.5.2.1/bin/emanote",
      "/nix/store/cdbfy4j0cl2lbn5a72kzh8hl1h0crw00-pre-commit-run",
      "/nix/store/md0y23sc68gq5j4br7ag7a3j8bgg1k02-emanote-docs-linkCheck",
      "/nix/store/ndxvfzirwzx2kg7vfp57r3n29r5ddixy-emanote-with-layers-docs/bin/emanote-with-layers-docs"
    ]
  }
}