Onboarding updates (#1967)

* Make onboarding line references dynamic and error if they aren't found
Fixes https://github.com/KittyCAD/modeling-app/issues/1918

* More clear and correct Sketch onboarding step
Fixes https://github.com/KittyCAD/modeling-app/issues/1790
Fixes https://github.com/KittyCAD/modeling-app/issues/1789

* Make sample code line references dynamic and error on app start if they break so we can know before release
Fixes https://github.com/KittyCAD/modeling-app/issues/1918

* Better error message for searchText failure

* JB onboarding feedback

* Make list more explicit, instruct to hold down key first

src/lib/exampleKcl.ts

@@ -34,5 +34,28 @@ const bracket = startSketchOn('XY')
   |> fillet({
        radius: filletR + thickness,
        tags: [getNextAdjacentEdge('outerEdge', %)]
-     }, %)
-`
+     }, %)`
+
+function findLineInExampleCode({
+  searchText,
+  example = bracket,
+}: {
+  searchText: string
+  example?: string
+}) {
+  const lines = example.split('\n')
+  const lineNumber = lines.findIndex((l) => l.includes(searchText)) + 1
+  if (lineNumber === 0) {
+    throw new Error(
+      `Could not find the line with search text "${searchText}" in the example code. Was it removed?`
+    )
+  }
+  return lineNumber
+}
+
+export const bracketWidthConstantLine = findLineInExampleCode({
+  searchText: 'const width',
+})
+export const bracketThicknessCalculationLine = findLineInExampleCode({
+  searchText: 'const thickness',
+})