update MIGRATING.md and README.md in preparation for v5 release (#3918)

* update MIGRATING.md and README.md in preparation for v5 release

Author: khanayan123

MIGRATING.md

@@ -4,6 +4,21 @@ This guide describes the steps to upgrade dd-trace from a major version to the
 next. If you are having any issues related to migrating, please feel free to
 open an issue or contact our [support](https://www.datadoghq.com/support/) team.
 
+## 4.0 to 5.0
+
+### Node 16 is no longer supported
+
+Node.js 16 has reached EOL in September 2023 and is no longer supported. Generally
+speaking, we highly recommend always keeping Node.js up to date regardless of
+our support policy.
+
+### Update `trace<T>` TypeScript declaration
+
+The TypeScript declaration for `trace<T>` has been updated to enforce 
+that calls to `tracer.trace(name, fn)` must receive a function which takes at least 
+the span object. Previously the span was technically optional when it should not have 
+been as the span must be handled.
+
 ## 3.0 to 4.0
 
 ### Node 14 is no longer supported

README.md

@@ -1,7 +1,8 @@
 # `dd-trace`: Node.js APM Tracer Library
 
-[![npm v4](https://img.shields.io/npm/v/dd-trace/latest?color=blue&label=dd-trace%40v4&logo=npm)](https://www.npmjs.com/package/dd-trace)
-[![npm v3](https://img.shields.io/npm/v/dd-trace/latest-node14?color=blue&label=dd-trace%40v3&logo=npm)](https://www.npmjs.com/package/dd-trace/v/latest-node12)
+[![npm v5](https://img.shields.io/npm/v/dd-trace/latest?color=blue&label=dd-trace%40v4&logo=npm)](https://www.npmjs.com/package/dd-trace)
+[![npm v4](https://img.shields.io/npm/v/dd-trace/latest-node16?color=blue&label=dd-trace%40v4&logo=npm)](https://www.npmjs.com/package/dd-trace/v/latest-node16)
+[![npm v3](https://img.shields.io/npm/v/dd-trace/latest-node14?color=blue&label=dd-trace%40v3&logo=npm)](https://www.npmjs.com/package/dd-trace/v/latest-node14)
 [![codecov](https://codecov.io/gh/DataDog/dd-trace-js/branch/master/graph/badge.svg)](https://codecov.io/gh/DataDog/dd-trace-js)
 
 <img align="right" src="https://user-images.githubusercontent.com/551402/208212084-1d0c07e2-4135-4c61-b2da-8f2fddbc66ed.png" alt="Bits the dog  JavaScript" width="200px"/>
@@ -28,24 +29,25 @@ Most of the documentation for `dd-trace` is available on these webpages:
 | [`v1`](https://github.com/DataDog/dd-trace-js/tree/v1.x) | ![npm v1](https://img.shields.io/npm/v/dd-trace/legacy-v1?color=white&label=%20&style=flat-square)     | `>= v12` | **End of Life** | 2021-07-13     | 2022-02-25  |
 | [`v2`](https://github.com/DataDog/dd-trace-js/tree/v2.x) | ![npm v2](https://img.shields.io/npm/v/dd-trace/latest-node12?color=white&label=%20&style=flat-square) | `>= v12` | **End of Life** | 2022-01-28     | 2023-08-15  |
 | [`v3`](https://github.com/DataDog/dd-trace-js/tree/v3.x) | ![npm v3](https://img.shields.io/npm/v/dd-trace/latest-node14?color=white&label=%20&style=flat-square) | `>= v14` | **Maintenance** | 2022-08-15     | 2024-05-15  |
-| [`v4`](https://github.com/DataDog/dd-trace-js/tree/v4.x) | ![npm v4](https://img.shields.io/npm/v/dd-trace/latest?color=white&label=%20&style=flat-square)        | `>= v16` | **Current**     | 2023-05-12     | Unknown     |
+| [`v4`](https://github.com/DataDog/dd-trace-js/tree/v4.x) | ![npm v4](https://img.shields.io/npm/v/dd-trace/latest-node16?color=white&label=%20&style=flat-square)        | `>= v16` | **Maintenance**     | 2023-05-12     | 2025-01-11     |
+| [`v5`](https://github.com/DataDog/dd-trace-js/tree/v5.x) | ![npm v5](https://img.shields.io/npm/v/dd-trace/latest?color=white&label=%20&style=flat-square)        | `>= v18` | **Current**     | 2024-01-11     | Unknown     |
 
-We currently maintain two release lines, namely `v3` and `v4`.
-Features and bug fixes that are merged are released to the `v4` line and, if appropriate, also the `v3` line.
+We currently maintain three release lines, namely `v5`, `v4` and `v3`.
+Features and bug fixes that are merged are released to the `v5` line and, if appropriate, also the `v4` & `v3` line.
 
-For any new projects it is recommended to use the `v4` release line:
+For any new projects it is recommended to use the `v5` release line:
 
 ```sh
 $ npm install dd-trace
 $ yarn add dd-trace
 ```
 
-However, existing projects that already use the `v3` release line, or projects that need to support EOL versions of Node.js, may continue to use these release lines.
+However, existing projects that already use the `v4` & `v3` release line, or projects that need to support EOL versions of Node.js, may continue to use these release lines.
 This is done by specifying the version when installing the package.
 
 ```sh
-$ npm install dd-trace@3
-$ yarn add dd-trace@3
+$ npm install dd-trace@4
+$ yarn add dd-trace@4
 ```
 
 Any backwards-breaking functionality that is introduced into the library will result in an increase of the major version of the library and therefore a new release line.