Use default export templates for HTML5

Changes Emscripten SDK version to match that used to compile the default export
templates used by Godot 3.5 (in this case 3.1.14 as can be seen here:
https://github.com/godotengine/build-containers/blob/3.5/Dockerfile.javascript).

This means we no longer need to compile custom export templates when
exporting HTML5 for Godot 3.5. Exports from other Godot versions may
requiring compiling the GDNative library with a different version of the
Emscripten SDK.

- Changes renderer from GLES3 -> GLES2 and reduces MSAA level to better
  support HTML5 export.
- Updates GitHub Action to export HTML5 and upload as a build artifact.
- Adds Cypress test to smoke test HTML5 export.

test/html5/.gitignore

@@ -0,0 +1,4 @@
+cypress-visual-screenshots/
+cypress/screenshots/
+cypress/videos/
+node_modules/

test/html5/cypress.config.js

@@ -0,0 +1,10 @@
+const { defineConfig } = require("cypress");
+const getCompareSnapshotsPlugin = require('cypress-image-diff-js/dist/plugin');
+
+module.exports = defineConfig({
+  e2e: {
+    setupNodeEvents(on, config) {
+      getCompareSnapshotsPlugin(on, config);
+    },
+  },
+});

test/html5/cypress/e2e/smoke_test.cy.js

@@ -0,0 +1,21 @@
+Cypress.on('window:before:load', win => {
+  cy.spy(win.console, 'error')
+  cy.spy(win.console, 'warn')
+  cy.spy(win.console, 'log')
+})
+
+describe('GodotXterm HTML5 export', () => {
+  it('Loads and runs without error', () => {
+    cy.visit('http://localhost:3000')
+    cy.compareSnapshot('menu', 0.9, {
+      limit: 100, delay: 200, timeout: 20000,
+    })
+    cy.get('body').type('{downArrow}{enter}')
+    cy.get('body').type('window.console.log("It works!"){enter}')
+    cy.window().then(win => {
+      cy.expect(win.console.error).to.have.callCount(0)
+      cy.expect(win.console.warn).to.have.callCount(0)
+      cy.expect(win.console.log).to.be.calledWith("It works!")
+    })
+  })
+})

test/html5/cypress/support/commands.js

@@ -0,0 +1,2 @@
+import compareSnapshotCommand from 'cypress-image-diff-js/dist/command';
+compareSnapshotCommand();

test/html5/cypress/support/e2e.js

@@ -0,0 +1 @@
+import './commands'

test/html5/package.json

@@ -0,0 +1,11 @@
+{
+  "scripts": {
+    "start": "npx serve ../../docs/demo",
+    "test": "npx cypress run"
+  },
+  "devDependencies": {
+    "cypress": "^10.4.0",
+    "cypress-image-diff-js": "^1.21.1",
+    "serve": "^14.0.1"
+  }
+}

test/html5/shell.nix

@@ -0,0 +1,14 @@
+let
+  pkgs = import <nixpkgs> {};
+in pkgs.mkShell {
+  buildInputs = with pkgs; [
+    cypress
+    nodejs-16_x
+    xsel
+  ];
+
+  shellHook = ''
+    export CYPRESS_INSTALL_BINARY=0
+    export CYPRESS_RUN_BINARY=${pkgs.cypress}/bin/Cypress
+  '';
+}