add composer support to this module

[hesco]

Have not yet tested the module itself, but I was able to successfully install the module with composer;

Lock file operations: 1 install, 2 updates, 0 removals

• Locking mattwire/webform_civicrm_esign (dev-feature/add_composer_support db1ae73)
  . . .
  Writing lock file Installing dependencies from lock file (including require-dev) Package operations: 1 install, 2 updates, 0 removals . . .
• Downloading mattwire/webform_civicrm_esign (dev-feature/add_composer_support db1ae73)
  Gathering patches for root package. Gathering patches for dependencies. This might take a minute. . . .
• Installing mattwire/webform_civicrm_esign (dev-feature/add_composer_support db1ae73): Extracting archive

with these lines added to my project's composer.json file:

"repositories": {
    "drupal": {
        "type": "composer",
        "url": "https://packages.drupal.org/8"
    },
    "webform_civicrm_esign": {
        "type": "vcs",
        "url": "https://github.com/hesco/webform_civicrm_esign.git"
    }
},
"require": {
    "mattwire/webform_civicrm_esign": "dev-feature/add_composer_support",
},

[mattwire]

Thanks @hesco