docs: split off a CONTRIBUTING.md and improve formatting, grammar, links

CONTRIBUTING.md

@@ -0,0 +1,32 @@
+# Contributing
+
+## Reporting bugs
+
+Report any bugs [in the GitHub Issue Tracker](https://github.com/ezolenko/rollup-plugin-typescript2/issues).
+
+Attach your `tsconfig.json`, `package.json` (for versions of dependencies), `rollup.config.js`, and anything else that could influence module resolution, ambient types, and TS compilation.
+
+Check if the problem is reproducible after running `npm prune` to clear any rogue types from `node_modules` (by default TS grabs _all_ ambient types).
+
+Check if you get the same problem with `clean` option set to `true` (might indicate a bug in the cache).
+
+If it makes sense, check if running `tsc` directly produces similar results.
+
+Attach plugin output with `verbosity` option set to 3 (this will list all files being transpiled and their imports).
+
+## Developing
+
+Use the [standard GitHub process](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/getting-started/about-collaborative-development-models#fork-and-pull-model) of forking, making a branch, and creating a PR when ready. Fix all linting problems (`npm run lint`) and fix any failed checks on the PR. Use an editor that supports [`editorconfig`](https://editorconfig.org/), or match the settings from [`.editorconfig`](./.editorconfig) manually.
+
+Fastest way to test changes is to do a self build; the plugin is part of its own build system:
+
+1. make changes
+1. run `npm run build` (uses last released version on npm)
+1. check that you get expected changes in `dist`
+1. run `npm run build-self` (uses fresh local build)
+1. check `dist` for the expected changes
+1. run `npm run build-self` _again_ to make sure plugin built by new version can still build itself
+
+If `build-self` breaks at some point, fix the problem and restart from the `build` step (a known good copy).
+
+This repo badly needs unit tests and integration tests with various scenarios and expected outcomes though.

README.md

@@ -213,32 +213,6 @@ TypeScript `2.4+`
 Rollup `1.26.3+`
 Node `6.4.0+` (basic es6 support)
 
-### Reporting bugs
+### Reporting bugs and Contributing
 
-Report any bugs on github: <https://github.com/ezolenko/rollup-plugin-typescript2/issues>.
-
-Attach your `tsconfig.json`, `package.json` (for versions of dependencies), rollup script and anything else that could influence module resolution, ambient types and typescript compilation.
-
-Check if problem is reproducible after running `npm prune` to clear any rogue types from npm_modules (by default typescript grabs all ambient types).
-
-Check if you get the same problem with `clean` option set to true (might indicate a bug in the cache).
-
-If makes sense, check if running `tsc` directly produces similar results.
-
-Attach plugin output with `verbosity` option set to 3 (this will list all files being transpiled and their imports).
-
-### Contributing
-
-Use the normal github process of forking, making a branch and creating a PR when ready. Fix all linting problems (run `npm lint`), fix any failed checks that are run on the PR (basically lint right now). Use an editor that supports editorconfig, or match the settings from `.editorconfig` file manually.
-
-Fastest way to test changes is to do a self build, the plugin is part of its own build system:
-- make changes
-- run `npm build` (uses last released version on npm)
-- check that you get expected changes in `dist`
-- run `npm build-self` (uses fresh local build)
-- check `dist` for the expected changes
-- run `npm build-self` _again_ to make sure plugin built by new version can still build itself
-
-If `build-self` breaks at some point, fix the problem and restart from `build` step (a known good copy).
-
-This repo badly needs unittests and integration tests with various scenarios and expected outcomes though.
+See [CONTRIBUTING.md](./CONTRIBUTING.md)