Add new helper method for escaping YAML text

... which can be useful when importing user strings in conf.yaml files,
etc.

Bug #14

kobweb/src/main/kotlin/com/varabyte/kobweb/cli/create/freemarker/FreemarkerState.kt

@@ -17,6 +17,7 @@ import com.varabyte.kobweb.cli.create.freemarker.methods.IsPositiveNumberMethod
 import com.varabyte.kobweb.cli.create.freemarker.methods.IsYesNoMethod
 import com.varabyte.kobweb.cli.create.freemarker.methods.NotMethod
 import com.varabyte.kobweb.cli.create.freemarker.methods.PackageToPathMethod
+import com.varabyte.kobweb.cli.create.freemarker.methods.EscapeYamlStringMethod
 import com.varabyte.kobweb.cli.create.freemarker.methods.YesNoToBoolMethod
 import com.varabyte.kobweb.common.error.KobwebException
 import com.varabyte.kobweb.common.path.invariantSeparatorsPath
@@ -59,6 +60,7 @@ class FreemarkerState(private val src: Path, private val dest: Path) {
         // endregion
 
         // region Converters
+        "escapeYamlString" to EscapeYamlStringMethod(), // Added in 0.9.17
         "fileToTitle" to FileToTitleMethod(),
         "fileToPackage" to FileToPackageMethod(),
         "not" to NotMethod(),

kobweb/src/main/kotlin/com/varabyte/kobweb/cli/create/freemarker/methods/YamlMethods.kt

@@ -0,0 +1,13 @@
+package com.varabyte.kobweb.cli.create.freemarker.methods
+
+/**
+ * Utility method for escaping relevant control characters before inserting text into a yaml string.
+ */
+class EscapeYamlStringMethod : SingleArgMethodModel() {
+    override fun exec(value: String): String {
+        return value
+            // Replace backslash first, else we'd modify any quote substitutions (e.g. '"' -> '\"' -> '\\"')
+            .replace("\\", """\\""")
+            .replace("\"", """\"""")
+    }
+}