feat(viewer): decode safe mathml

[icaparros-at-wiris]

Description

This PR update the viewer in order to decode Safe MathML to MathML. This is necesary for moodle filter plugin as the safe mathml rendering from Moodle is not working when using the new viewer.

Steps to reproduce

1. Use wiris-moodle-docker and deploy MOODLE_403_STABLE.
2. Configure MathType filter to use the render option: Client.
3. If you have moodle volume on /html/var/MOODLE_403_STABLE you can use this webpack.config.js example to build viewer directly to the moodle-filter_wiris plugin:

const path = require('path');

module.exports = (config, context) => {
  return {
    entry: './src/app.ts',
    mode: 'none',
    devtool: 'inline-source-map',
    module: {
      rules: [
        {
          test: /\.tsx?$/,
          use: 'ts-loader',
          exclude: /node_modules/,
        },
        {
          test: /\.js$/,
          exclude: /node_modules/,
          use: ['babel-loader']
        },
      ],
    },
    resolve: {
      extensions: ['.tsx', '.ts', '.js'],
    },
    output: {
      filename: 'WIRISplugins.js',
      path: '/var/www/MOODLE_403_STABLE/filter/wiris/render',
    },
    devServer: {
      devMiddleware: {
        writeToDisk: true,
      },
      static:  './',
      hot: true,
      port: 8001,
      open: true,
    },
    optimization: {
      minimize: false, // enabling this reduces file size and readability
    },
  }
};

4. On html-integrations run the next commands to build the viewer:

yarn
nx build viewer

5. Create a course or task with some Math formula with on the description.
6. Check If is rendered correctly.

---

#taskid 40011