Add support for Fulcio and Rekor, and --sign-by-sigstore=param-file

(skopeo copy) and (skopeo sync) now support --sign-by-sigstore=param-file,
using the containers-sigstore-signing-params.yaml(5) file format.

That notably adds support for Fulcio and Rekor signing.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/github.com/go-openapi/jsonreference/.golangci.yml

@@ -0,0 +1,41 @@
+linters-settings:
+  govet:
+    check-shadowing: true
+  golint:
+    min-confidence: 0
+  gocyclo:
+    min-complexity: 30
+  maligned:
+    suggest-new: true
+  dupl:
+    threshold: 100
+  goconst:
+    min-len: 2
+    min-occurrences: 4
+linters:
+  enable-all: true
+  disable:
+    - maligned
+    - lll
+    - gochecknoglobals
+    - godox
+    - gocognit
+    - whitespace
+    - wsl
+    - funlen
+    - gochecknoglobals
+    - gochecknoinits
+    - scopelint
+    - wrapcheck
+    - exhaustivestruct
+    - exhaustive
+    - nlreturn
+    - testpackage
+    - gci
+    - gofumpt
+    - goerr113
+    - gomnd
+    - tparallel
+    - nestif
+    - godot
+    - errorlint