fix(README): add readme to epsagon/web (#46)

packages/web/README.md

@@ -0,0 +1,124 @@
+
+<p align="center">
+  <a href="https://epsagon.com" target="_blank" align="center">
+    <img src="https://cdn2.hubspot.net/hubfs/4636301/Positive%20RGB_Logo%20Horizontal%20-01.svg" width="300">
+  </a>
+  <br />
+</p>
+
+# Epsagon Tracing for Web
+
+This package provides tracing to front end of web applications for the collection of distributed tracing and performance metrics in [Epsagon](https://app.epsagon.com/?utm_source=github).
+
+## Contents
+
+- [Installation](#installation)
+- [Usage](#usage)
+  - [Custom Tags](#custom-tags)
+- [Configuration](#configuration)
+  - [Trace Header Propagation](#trace-header-propagation)
+- [Getting Help](#getting-help)
+- [Opening Issues](#opening-issues)
+- [License](#license)
+
+## Installation
+
+To install Epsagon, simply run:
+```sh
+npm install @epsagon/web
+```
+
+## Usage
+
+To initialize the tracer, import the SDK and call the init function before the start of your project.
+
+```javascript
+import epsagon from '@epsagon/web'
+
+epsagon.init({
+  token: 'epsagon-token',
+  appName: 'app-name-stage',
+})
+```
+
+## Custom Tags
+
+To add additional information to spans there are two methods available. Batch add user identity information with the ```epsagon.identity``` function, or use the ```epsagon.tag``` function to add your own custom information.
+
+Options for ```epsagon.identify``` include { userId, userName, userEmail, companyId, companyName }.
+
+```js
+epsagon.identify({
+  userId: '7128f1a08a95e46c', 
+  userName: 'John Doe', 
+  userEmail: 'john@doe.com',
+  companyId: 'fcffa7328813e4', 
+  companyName: 'Epsagon'
+})
+
+```
+
+Custom tags can only be added one at a time by passing a key and value to the tag function.
+
+```js
+epsagon.tag('PurchaseId', '2ef5b4bfdd')
+```
+
+## Configuration
+
+Advanced options can be configured as a parameter to the init() method.
+
+|Parameter          |Type   |Default      |Description                                                                        |
+|-------------------|-------|-------------|-----------------------------------------------------------------------------------|
+|token              |String |-            |Epsagon account token                                                              |
+|appName            |String |`Epsagon Application`|Application name that will be set for traces                                       |
+|collectorURL       |String |-|The address of the trace collector to send trace to                                       |
+|metadataOnly       |Boolean|`false`       |Whether to send only the metadata (`true`) or also the payloads (`false`)          |
+|propagateTraceHeaderUrls       |Array|`*`       |Which outgoing requests to add traceparent headers to. Defaults to all.          |
+|urlPatternsToIgnore            |Array|[]        |Which outgoing requests to ignore (and not add traceparent to. Default to []   |
+|isEpsagonDisabled       |Boolean|`false`       |A flag to completely disable Epsagon (can be used for tests or locally)         |
+|epsagonDebug       |Boolean|`false`       |Enable debug prints for troubleshooting. Note: if this flag is true, this will override the logLevel|
+|logLevel       |String|`INFO`       |The default Log level. Could be one of: ```DEBUG```, ```INFO```, ```WARN```, ```ERROR```, ```ALL```.|
+
+
+### Trace Header Propagation
+By default all outgoing requests will be added with a `traceparent` header which allows Epsagon to connect the front end trace to the backend traces. Some external services will not accept a traceparent header on request. If you need to limit the traceparent headers to requests to internal services, pass in an array of the hosts you do want to connect to in the propagateTraceHeaderUrls param in the config.
+
+```javascript
+import epsagon from '@epsagon/web'
+
+epsagon.init({
+  token: 'epsagon-token',
+  appName: 'app-name-stage',
+  propagateTraceHeaderUrls: ['localhost', 'sub.example.com'],
+  urlPatternsToIgnore: [".*example.*", ".*abc.*"]  
+})
+```
+
+## Getting Help
+
+If you have any issue around using the library or the product, please don't hesitate to:
+
+* Use the [documentation](https://docs.epsagon.com).
+* Use the help widget inside the product.
+* Open an issue in GitHub.
+
+
+## Opening Issues
+
+If you encounter a bug with the Epsagon library, we want to hear about it.
+
+When opening a new issue, please provide as much information about the environment:
+* Library version, Node.js runtime version, dependencies, etc.
+* Snippet of the usage.
+* A reproducible example can really help.
+
+The GitHub issues are intended for bug reports and feature requests.
+For help and questions about Epsagon, use the help widget inside the product.
+
+
+## License
+
+Provided under the MIT license. See LICENSE for details.
+
+Copyright 2021, Epsagon