Remove outdated GHC section; fold in tech-choices.md

Author: chreekat

CONTRIBUTING.md

@@ -140,23 +140,16 @@ field. All `.hs` files are shown in the list of files for the
 example. The `index.md` file should explain how the files illustrate
 the message.
 
-## Reference: How to Document a GHC Error Code
-
-[FIXME this section may be irrelevant or out of date.]
-
-To document a new error code, the following workflow can be convenient.
- 1. Choose a code that you'd like to document, say `GHC-123`
- 2. [FIXME: This is not an actionable step] One of the following modules in the `compiler` directory of the GHC source tree will have a method called `diagnosticCode` in the instance of `Diagnostic`:
-   * `GHC.Tc.Errors.Ppr` (error constructors starting `Tc`)
-   * `GHC.Driver.Errors.Ppr` (error constructors starting `Driver`)
-   * `GHC.Parser.Errors.Ppr` (error constructors starting `Pc`)
-   * `GHC.HsToCore.Errors.Ppr` (error constructors starting `Ds`)
- 3. Once the code has been found, identify the error datatype constructor that produces it.
- 4. The documentation for the constructor will be in one of the following modules. Read the Haddock for an explanation of the error's meaning:
-   * `GHC.Tc.Errors.Types`
-   * `GHC.Driver.Errors.Types`
-   * `GHC.Parser.Errors.Types`
-   * `GHC.HsToCore.Errors.Types`
- 5. Find the pretty-printer for the error constructor in the `X.Ppr` module. This will give an idea of how the message looks when rendered.
- 6. Grep the `testsuite` directory for the error text to find examples that trigger the error.
- 7. Follow the instructions below to create a page with an explanation and examples.
+## Reference: Technology choices
+
+The website generated by `message-index` uses a few JS components.
+
+ - [highlight.js](https://highlightjs.org/) for highlighting blocks of code. [License: BSD 3-Clause](https://github.com/highlightjs/highlight.js/blob/main/LICENSE).
+ - [TableFilter](http://www.tablefilter.com/) for the filtering functionality in the error message table. [License: MIT](https://github.com/koalyptus/TableFilter/blob/master/LICENSE).
+
+Generally speaking, we choose technology for this site based on the following criteria:
+
+ * The build process for the site should be simple, relying on no build tools or package managers aside from `cabal` or `stack`
+ * CSS and Javascript code should be straightforward to maintain by someone who has only rudimentary front-end development skills
+ * The generated site should consist only of static files that can be hosted anywhere
+ * URLs should be predictable, and easy for external tools to generate (e.g. so IDEs can link to error documentation)