feat: add support for title option

[BrunnerLivio]

Description

conventional-changelog-angular offers an optional configuration in the header.hbs for titles.

This pull request exposes this option.

Motivation

I wanted to have custom auto-generated titles in my release-notes so they're more memorable. I wanted to use Moniker in order to generate a random word, like so:

const Moniker = require("moniker");

const title = Moniker.generator([Moniker.adjective, Moniker.noun], { glue: ' ' }).choose();
console.log('Creating release: ' + title);

module.exports = {
  plugins: [
    "@semantic-release/commit-analyzer",
    [
      "@semantic-release/release-notes-generator",
      {
        preset: 'angular',
        title,
      },
    ],
...
  ],
};

... which results in:

# 1.2.0 (https://MY_DOMAIN.COM/compare/v1.1.0...v1.2.0) "barbarous flight" (2020-10-05)

### Bug Fixes

    * add release titles (2d47e7f (https://MY_DOMAIN.COM/commit/2d47e7f3d3ac322cd25f7f24f8c28b202b4ae6bc))

### Features

    * a new release (ffb348b (https://MY_DOMAIN.COM/commit/ffb348bc362fc8f1a741df6cc849c3120fa5cefd))

[BrunnerLivio]

A workaround for this PR currently is by overwriting the default partial provided by whatever preset you are using. For example for Angular preset:

const Moniker = require("moniker");

const title = Moniker.generator([Moniker.adjective, Moniker.noun], { glue: ' ' }).choose();

module.exports = {
  plugins: [
    "@semantic-release/commit-analyzer",
    [
      "@semantic-release/release-notes-generator",
      {
        preset: 'angular',
        writerOpts: {
          headerPartial: `{{#if isPatch~}}
  ##
{{~else~}}
  #
{{~/if}} {{#if @root.linkCompare~}}
  [{{version}}](
  {{~#if @root.repository~}}
    {{~#if @root.host}}
      {{~@root.host}}/
    {{~/if}}
    {{~#if @root.owner}}
      {{~@root.owner}}/
    {{~/if}}
    {{~@root.repository}}
  {{~else}}
    {{~@root.repoUrl}}
  {{~/if~}}
  /compare/{{previousTag}}...{{currentTag}})
{{~else}}
  {{~version}}
{{~/if}}
 ${title}
{{~#if date}} ({{date}})
{{/if}}`
        }
      },
    ],
...
  ],
};