(new definition) add mjml (mjml.io) types (#25217)

* add mjml (mjml.io) types

* update mjml definition, actually verify linter runs, be more explicit in re: error types

* mjml: int -> number.  why does lint pass w/ 'int'? ah well.

* per @plantain-00 CR

types/mjml/index.d.ts

@@ -0,0 +1,29 @@
+// Type definitions for mjml 4.0
+// Project: https://github.com/mjmlio/mjml
+// Definitions by: aahoughton <https://github.com/aahoughton>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+interface MJMLParsingOpts {
+    fonts?: { [key: string]: string; };
+    keepComments?: boolean;
+    beautify?: boolean;
+    minify?: boolean;
+    validationLevel?: 'strict' | 'soft' | 'skip';
+    filePath?: boolean;
+}
+
+interface MJMLParseError {
+    line: number;
+    message: string;
+    tagName: string;
+    formattedMessage: string;
+}
+
+interface MJMLParseResults {
+    html: string;
+    errors: MJMLParseError[];
+}
+
+declare function mjml2html(inp: string, opts?: MJMLParsingOpts): MJMLParseResults;
+
+export = mjml2html;

types/mjml/mjml-tests.ts

@@ -0,0 +1,10 @@
+import mjml2html = require('mjml');
+
+const simple_test = mjml2html("<mjml>");
+const html = simple_test.html;
+const errors = simple_test.errors;
+let formattedMessage = errors[0].formattedMessage;
+formattedMessage = "force string test";
+
+const minimal_opts_test = mjml2html("<mjml>", {beautify: true});
+const validation_level_test = mjml2html("<mjml>", {validationLevel: "strict"});

types/mjml/tsconfig.json

@@ -0,0 +1,23 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "strictFunctionTypes": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "mjml-tests.ts"
+    ]
+}

types/mjml/tslint.json

@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }