fix: make pattern for finding CHANGELOG sections work for non anchors (#292)

Author: edahlseng

lib/lifecycles/changelog.js

@@ -23,8 +23,9 @@ function outputChangelog (args, newVersion) {
     var header = '# Change Log\n\nAll notable changes to this project will be documented in this file. See [standard-version](https://github.com/conventional-changelog/standard-version) for commit guidelines.\n'
     var oldContent = args.dryRun ? '' : fs.readFileSync(args.infile, 'utf-8')
     // find the position of the last release and remove header:
-    if (oldContent.indexOf('<a name=') !== -1) {
-      oldContent = oldContent.substring(oldContent.indexOf('<a name='))
+    const changelogSectionRegExp = /<a name=|##? \[?[0-9]+\.[0-9]+\.[0-9]+\]?/
+    if (oldContent.search(changelogSectionRegExp) !== -1) {
+      oldContent = oldContent.substring(oldContent.search(changelogSectionRegExp))
     }
     var content = ''
     var context