Add pixel comparison mode to Compare tool (#6109)

Co-authored-by: Anthony Stirling <[email protected]>
Co-authored-by: EthanHealy01 <[email protected]>

frontend/public/locales/en-GB/translation.toml

@@ -2810,6 +2810,33 @@ confirmTitle = "Re-run comparison?"
 unlinkedBody = "Tip: Arrow Up/Down scroll both panes; panning only moves the active pane."
 unlinkedTitle = "Independent scroll & pan enabled"
 
+[compare.mode]
+pixel = "Pixel Comparison"
+text = "Text Comparison"
+
+[compare.pixel]
+base = "Original"
+changed = "changed"
+comparison = "Edited"
+diff = "Differences"
+diffOnly = "Diff only"
+missingInBase = "Missing in original"
+missingInComparison = "Missing in edited"
+overall = "overall"
+overlay = "Overlay"
+pageLabel = "Page"
+pagesChanged = "pages changed"
+sideBySide = "Side-by-side"
+sizeMismatch = "Size mismatch"
+summaryTitle = "Pixel comparison"
+
+[compare.pixel.warnings]
+noPages = "One or both documents have no pages."
+pageCountMismatch = "Page count mismatch: original has {{base}} page(s), edited has {{comparison}}. Extra pages are shown one-sided and marked as fully removed/added."
+
+[compare.pixel.errors]
+canvasContextUnavailable = "Unable to acquire 2D canvas context for pixel comparison."
+
 [compare.too.dissimilar]
 message = "These documents appear highly dissimilar. Comparison was stopped to save time."