fix: Escape scoped package names in PR bodies (#568)

GitHub attempts to autolink any @user mention and this causes problems when we use scoped npm modules like `@types/gulp`. This escapes such package names with a zero width space to fool GitHub’s parser.

Fixes #518

lib/config/templates/default/pr-body.hbs

-This {{#if isGitHub}}Pull{{else}}Merge{{/if}} Request {{#if isRollback}}rolls back{{else}}updates{{/if}} dependency [{{depName}}]({{repositoryUrl}}) from version `{{currentVersion}}` to `{{newVersion}}`{{#if isRollback}}. This is necessary and important because version `{{currentVersion}}` cannot be found in the npm registry - probably because of it being unpublished.{{/if}}
+This {{#if isGitHub}}Pull{{else}}Merge{{/if}} Request {{#if isRollback}}rolls back{{else}}updates{{/if}} dependency {{#if repositoryUrl}}[{{depName}}]({{repositoryUrl}}){{else}}`depName`{{/if}} from version `{{currentVersion}}` to `{{newVersion}}`{{#if isRollback}}. This is necessary and important because version `{{currentVersion}}` cannot be found in the npm registry - probably because of it being unpublished.{{/if}}
 {{#if releases.length}}
 
 {{#if schedule}}

lib/workers/pr/index.js

@@ -114,7 +114,9 @@ async function ensurePr(inputConfig, logger, errors, warnings) {
   }
 
   const prTitle = handlebars.compile(config.prTitle)(config);
-  const prBodyMarkdown = handlebars.compile(config.prBody)(config);
+  let prBodyMarkdown = handlebars.compile(config.prBody)(config);
+  const atUserRe = /@([a-z]+\/[a-z]+)/;
+  prBodyMarkdown = prBodyMarkdown.replace(atUserRe, '@​$1');
   const prBody = converter.makeHtml(prBodyMarkdown);
 
   try {

test/workers/package/__snapshots__/index.spec.js.snap

@@ -110,7 +110,7 @@ This {{#if isGitHub}}PR{{else}}MR{{/if}} has been generated by [Renovate Bot](ht
     "labels": Array [],
     "lazyGrouping": true,
     "message": "Failed to look up dependency",
-    "prBody": "This {{#if isGitHub}}Pull{{else}}Merge{{/if}} Request {{#if isRollback}}rolls back{{else}}updates{{/if}} dependency [{{depName}}]({{repositoryUrl}}) from version \`{{currentVersion}}\` to \`{{newVersion}}\`{{#if isRollback}}. This is necessary and important because version \`{{currentVersion}}\` cannot be found in the npm registry - probably because of it being unpublished.{{/if}}
+    "prBody": "This {{#if isGitHub}}Pull{{else}}Merge{{/if}} Request {{#if isRollback}}rolls back{{else}}updates{{/if}} dependency {{#if repositoryUrl}}[{{depName}}]({{repositoryUrl}}){{else}}\`depName\`{{/if}} from version \`{{currentVersion}}\` to \`{{newVersion}}\`{{#if isRollback}}. This is necessary and important because version \`{{currentVersion}}\` cannot be found in the npm registry - probably because of it being unpublished.{{/if}}
 {{#if releases.length}}
 
 {{#if schedule}}