build: generate changelog automatically

This issue of generating automated changelog can be separated into two parts:

1. Making sure each MR contains information that can be used for generating a changelog
2. Collecting the aforementioned information and creating changelog at the time of release

This MR handles the second part. It requires the rules enforced by !85 (merged).

Problem

In !85 (merged) we started enforcing the conventional commit message format. This MR uses these formatted commits to generate a changelog.

Solution

We include the conventional-changelog dependency in our project and run conventional-changelog -p angular -i CHANGELOG.md -s && git add CHANGELOG.md before we tag a new version of the extension.

This will automatically take the changes since the last tag and generates a changelog in the same format as the one in gitlab-ui.

Example

1. I created two example commits

   • feat(statusbar): add logo to the statusbar
   • fix(treeview): removing faulty issues

2. Running npm version minor produced the following commit:

commit 14c1b180a150be680233335c8ac3a6f2a18cbd9f
Author: Tomas Vik <tvik@gitlab.com>
Date:   Tue Aug 11 12:44:14 2020 +0200

    3.3.0

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a3bc1e0..a9e144f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,17 @@
+# [3.3.0](https://gitlab.com/gitlab-org/gitlab-vscode-extension/compare/v3.2.0...v3.3.0) (2020-08-11)
+
+
+### Bug Fixes
+
+* **treeview:** removing faulty issues ([fbc81ea](https://gitlab.com/gitlab-org/gitlab-vscode-extension/commit/fbc81ea900edec83504921ea047b04b552206513))
+
+
+### Features
+
+* **statusbar:** add logo to the statusbar ([efaeb8f](https://gitlab.com/gitlab-org/gitlab-vscode-extension/commit/efaeb8f92711e172892ae51af474f6bd0285a83e))
+
+
+
 # CHANGELOG
 
 ## v3.2.0 - 2020-08-03
diff --git a/package-lock.json b/package-lock.json
index 410a02f..f68184e 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "gitlab-workflow",
-  "version": "3.2.0",
+  "version": "3.3.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index 3f26126..a91cc04 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
   "name": "gitlab-workflow",
   "displayName": "GitLab Workflow",
   "description": "GitLab VSCode integration",
-  "version": "3.2.0",
+  "version": "3.3.0",
   "publisher": "GitLab",
   "license": "MIT",
   "repository": {

Future: semantic-release

There is a potential of configuring the semantic-release toolchain to completely automate the release process. The semantic-release uses the conventional commits and and conventional-changelog module under the hood. That means we are ready for using semantic-release later on.

The main problem is that the semantic-release doesn't currently support releasing VS Code extensions easily. There is an unofficial plugin raix/semantic-release-vsce but it doesn't seem too well maintained and only supports Microsoft marketplace (no open-vsx).

We might be able to use the exec plugin and write our custom scripts in the future.

Note: I had to run npm audit fix to fix some known vulnerabilities in the conventional-changelog dependencies.

Part of #198 (closed)