Add documentation for --failOnContentCheck and update CLI options in docs (#869)

Related to #860 

This will give us something we can link to from Browsertrix/the
Browsertrix User Guide for up-to-date information on this option.

docs/docs/user-guide/behaviors.md

@@ -268,3 +268,26 @@ Some of these functions which may be of use to behaviors authors are:
 - `getState`: increment a state counter and return all state counters + string message
 
 More detailed references will be added in the future.
+
+## Fail On Content Check
+
+In Browsertrix Crawler 1.7.0 and higher, the `--failOnContentCheck` option will result in a crawl failing if a behavior detects the presence or absence of certain content on a page in its `awaitPageLoad()` callback. By default, this is used to fail a crawl if site-specific behaviors determine that the user is not logged in on the following sites:
+
+- Facebook
+- Instagram
+- TikTok
+- X
+
+It is also used to fail crawls with YouTube videos if one of the videos is found not to play.
+
+It is possible to add content checks to custom behaviors. To do so, include an `awaitPageLoad` method on the behavior and use the `ctx.Lib` function `assertContentValid` to check for content and fail the behavior with a specified reason if it is not found.
+
+For an example, see the following `awaitPageLoad` example from the site-specific behavior for X:
+
+```javascript
+async awaitPageLoad(ctx: any) {
+  const { sleep, assertContentValid } = ctx.Lib;
+  await sleep(5);
+  assertContentValid(() => !document.documentElement.outerHTML.match(/Log In/i), "not_logged_in");
+}
+```

docs/docs/user-guide/cli-options.md

@@ -261,6 +261,10 @@ Options:
                                             ailOnFailedSeed may result in crawl
                                             failing due to non-200 responses
                                                       [boolean] [default: false]
+      --failOnContentCheck                  If set, allows for behaviors to fail
+                                             a crawl with custom reason based on
+                                             content (e.g. logged out)
+                                                      [boolean] [default: false]
       --customBehaviors                     Custom behavior files to inject. Val
                                             id values: URL to file, path to file
                                             , path to directory of behaviors, UR
@@ -272,6 +276,10 @@ Options:
                                             git+https://git.example.com/repo.git
                                             ?branch=dev&path=some/dir"
                                                            [array] [default: []]
+      --saveStorage                         if set, will store the localStorage/
+                                            sessionStorage data for each page as
+                                             part of WARC-JSON-Metadata field
+                                                                       [boolean]
       --debugAccessRedis                    if set, runs internal redis without
                                             protected mode to allow external acc
                                             ess (for debugging)        [boolean]