Command to open release notes

[Jakeeyturner]

Description

I thought I'd already created this issue, but apparently not...

We should have a command to open the recent release notes.

We might possibly want an icon which brings them up as well.

Expected Behavior

Actual Behavior

Possible Fix

In extension.ts we should take out:

try {

    // Open up Release Notes markdown
    const getExtensionPath: string = ExtensionUtil.getExtensionPath();
    const releaseNotes: string = path.join(getExtensionPath, 'RELEASE-NOTES.md');
    const uri: vscode.Uri = vscode.Uri.file(releaseNotes);

    await vscode.commands.executeCommand('markdown.showPreview', uri);
} catch (error) {
    outputAdapter.log(LogType.ERROR, `Unable to open release notes: ${error.toString()}`);
}

Make it a separate command, and then call it from here.

Steps to Reproduce

Existing issues

• Stack Overflow issues
• GitHub Issues

Log File

Your Environment

• IBM Blockchain Platform Extension Version:
• Visual Studio Code version:
• Environment name and version (e.g. Node.js v8.12.0, npm v6.4.1):
• Operating System and version:
• Link to your project: