feat(js): Document missing options for http integration (#15815)

## DESCRIBE YOUR PR

Adds 3 missing options to the documentation:

1. spans - Controls whether spans are created for outgoing HTTP requests
2. disableIncomingRequestSpans - Disables spans for incoming requests
3. sessionFlushingDelayMS - Controls session flushing interval

## IS YOUR CHANGE URGENT?  

Help us prioritize incoming PRs by letting us know when the change needs
to go live.
- [ ] Urgent deadline (GA date, etc.): <!-- ENTER DATE HERE -->
- [ ] Other deadline: <!-- ENTER DATE HERE -->
- [ ] None: Not urgent, can wait up to 1 week+


Related issue:
getsentry/sentry-javascript#18490

Author: andreiborza

docs/platforms/javascript/common/configuration/integrations/http.mdx

@@ -50,17 +50,24 @@ Sentry.init({
 
 ### `breadcrumbs`
 
-_Type: `boolean`_
+_Type: `boolean`_ (Defaults to `true`)
 
 If set to false, no breadcrumbs will be captured.
 
+### `spans`
+
+_Type: `boolean`_ (Defaults to `false`)
+
+If set to true, spans will be created for outgoing HTTP requests.
+
 ### `maxIncomingRequestBodySize`
 
 _Type: `'none' | 'small' | 'medium' | 'always'`_ (Defaults to `'medium'`)
 
 Controls the maximum size of incoming HTTP request bodies attached to events.
 
 Available options:
+
 - 'none': No request bodies will be attached
 - 'small': Request bodies up to 1,000 bytes will be attached
 - 'medium': Request bodies up to 10,000 bytes will be attached (default)
@@ -108,6 +115,21 @@ _Type: `boolean`_ (Defaults to `true`)
 
 If set to true, no spans will be captured for static assets like images, fonts, and other files.
 
+### `disableIncomingRequestSpans`
+
+_Type: `boolean`_
+
+If set to true, no spans will be generated for incoming requests.
+
+### `dropSpansForIncomingRequestStatusCodes`
+
+_Type: `(number | [number, number])[]`_ (Defaults to `[[401, 404], [301, 303], [305, 399]]`)
+
+Do not capture spans for incoming HTTP requests with the given status codes.
+By default, spans with some 3xx and 4xx status codes are ignored.
+Expects an array that can contain individual status codes (numbers) or ranges (2-element arrays of `[start, end]` where both start and end are inclusive).
+
+For example, `[[300, 399], 404]` would ignore all 3xx status codes (300-399 inclusive) and 404 status codes.
 
 ### `trackIncomingRequestsAsSessions`
 
@@ -116,6 +138,12 @@ _Type: `boolean`_ (Defaults to `true`)
 Determines whether the integration should create [Sessions](/product/releases/health/#sessions) for incoming requests to track the health and crash-free rate of your releases in Sentry.
 Read more about [Release Health](/product/releases/health/).
 
+### `sessionFlushingDelayMS`
+
+_Type: `number`_ (Defaults to `60000`)
+
+The delay in milliseconds before sessions are flushed as a session aggregate. This controls how frequently session data is sent to Sentry.
+
 ### `instrumentation`
 
 You can also pass some hooks through to the [underlying OpenTelemetry Instrumentation](https://www.npmjs.com/package/@opentelemetry/instrumentation-http):