Provide a way to use hmr by default for a project

[rosen-vladimirov]

Is your feature request related to a problem? Please describe.
Currently HMR requires passing --hmr option on every command. When I forget to pass it, the application is rebuild and after that I have to stop the command and execute it again, which triggers another rebuild. This slows down my application development.

Describe the solution you'd like
Provide an easy way to have hmr working out-of-the-box, i.e. when I execute tns run [<platform>] hmr to be set by default. It would be great if this feature is enabled by default for newly created projects and if I'm able to enable it for old projects. For example, it can be handled by handling having a property in nsconfig.json that enables HMR.

Describe alternatives you've considered
No

Additional context
HMR provides the best development experience, i.e. application is not restarted when you change .ts, .js, .html, .xml, .css, .scss file in the app, so this improves the experience with several seconds for each change. Also the changes are synced much faster than in normal livesync process.

[jlooper]

Yes, but we need to make sure all the 'flavors' of NS work nicely with HMR...working on the Vue piece of this

[NathanWalker]

As long as HMR works reliably and predictably. I'm still seeing oddities with Angular --hmr enabled. Can share on screen if need be (ping via Slack if needed)

[triniwiz]

As @jlooper said once it works on all flavors 😄 ....

[miroslavaivanova]

Acceptance Criteria:

• expected error: --hmr --release
• expected error: --hmr --no-bundle
• without useLegacyWorkflow in nsconfig: old behaviour
• without nsconfig: old behaviour
• useLegacyWorkflow: true -> old behaviour
• useLegacyWorkflow: false -> new behaviour: hmr + webpack
• useLegacyWorkflow: false -> you can stop with: --no-hmr or/and --no-bundle
• useLegacyWorkflow: false + --release -> webpack build without hmr