Update contributing guide and PR template (#7008)

* Update contributing guide

* Refactor pull request template

* Reword PR template a bit

* Update CONTRIBUTING.md

Co-authored-by: Reilly Wood <26268125+rgwood@users.noreply.github.com>

* Reformulate

* Make "Before Submitting" a top-level header

* Add review requirement to After Submitting

* Reformulate

* Update .github/pull_request_template.md

Co-authored-by: Dan Davison <dandavison7@gmail.com>

* Reformulate contributing guide

Co-authored-by: Reilly Wood <26268125+rgwood@users.noreply.github.com>
Co-authored-by: Dan Davison <dandavison7@gmail.com>

.github/pull_request_template.md

@@ -1,6 +1,12 @@
 # Description
 
-(Description of your pull request goes here. **Provide examples and/or screenshots** unless the change is trivial)
+(Description of your pull request goes here. **Provide examples and/or screenshots** if your changes affect the user experience.)
+
+# Major Changes
+
+If you're considering making any major change to nushell, before starting work on it, seek feedback from regular contributors and get approval for the idea from the core team either on [Discord](https://discordapp.com/invite/NtAbbGn) or [GitHub issue](https://github.com/nushell/nushell/issues/new/choose).
+Making sure we're all on board with the change saves everybody's time.
+Thanks!
 
 # Tests + Formatting
 
@@ -15,9 +21,6 @@ Make sure you've run and fixed any issues with these commands:
 - `cargo clippy --workspace --features=extra -- -D warnings -D clippy::unwrap_used -A clippy::needless_collect` to check that you're using the standard code style
 - `cargo test --workspace --features=extra` to check that all tests pass
 
-# User-Facing Changes
+# After Submitting
 
-If you're making changes that will affect the user experience of Nushell (ex: adding/removing a command, changing an input/output type, adding a new flag):
-
-- Get another regular contributor to review the PR before merging
-- Make sure that there is an entry in the documentation (https://github.com/nushell/nushell.github.io) for the feature, and update it if necessary
+* Help us keep the docs up to date: If your PR affects the user experience of Nushell (adding/removing a command, changing an input/output type, etc.), make sure the changes are reflected in the documentation (https://github.com/nushell/nushell.github.io) after the PR is merged.

CONTRIBUTING.md

@@ -1,8 +1,23 @@
 # Contributing
 
-Welcome to Nushell!
+Welcome to Nushell and thank you for considering contributing!
 
-To get live support from the community see our [Discord](https://discordapp.com/invite/NtAbbGn), [Twitter](https://twitter.com/nu_shell) or file an issue or feature request here on [GitHub](https://github.com/nushell/nushell/issues/new/choose)!
+## Review Process
+
+First of all, before diving into the code, if you want to create a new feature, change something significantly, and especially if the change is user-facing, it is a good practice to first get an approval from the core team before starting to work on it.
+This saves both your and our time if we realize the change needs to go another direction before spending time on it.
+So, please, reach out and tell us what you want to do.
+This will significantly increase the chance of your PR being accepted.
+
+The review process can be summarized as follows:
+1. You want to make some change to Nushell that is more involved than simple bug-fixing.
+2. Go to [Discord](https://discordapp.com/invite/NtAbbGn) or a [GitHub issue](https://github.com/nushell/nushell/issues/new/choose) and chat with some core team members and/or other contributors about it.
+3. After getting a green light from the core team, implement the feature, open a pull request (PR) and write a concise but comprehensive description of the change.
+4. If your PR includes any use-facing features (such as adding a flag to a command), clearly list them in the PR description.
+5. Then, core team members and other regular contributors will review the PR and suggest changes.
+6. When we all agree, the PR will be merged.
+7. If your PR includes any user-facing features, make sure the changes are also reflected in [the documentation](https://github.com/nushell/nushell.github.io) after the PR is merged.
+8. Congratulate yourself, you just improved Nushell! :-)
 
 ## Developing