Firefox Support Docs (#2225)

* Initial commits for Firefox support

* Add 'isBrowser' and 'isBrowserType' to docs (introduced in Firefox PR)

* packagelock

* Remove 'firefox support' from roadmap + tradoff of no cross browser support

* Add notes about chromeWebSecurity only working in Chrome family browsers.

* add cross-browser guide

* Add 'cross-browser' to textlintrc

* Update use of 'cross-browser' hyphenated.

* minor editing / mostly fixing broken links and 'url' links

* remove references to open --browser flag

* add helpful info on cron expressions

* rename cross browser guide

* add localized titles for cross browser guide

* fix typo

* package-lock again

* add cross browser testing to russian titles

* add isBrowser pages to russian titles

Co-authored-by: Amir Rustamzadeh <[email protected]>

.textlintrc

@@ -22,6 +22,7 @@
         "BrowserStack",
         ["^chai", "Chai"],
         ["^chai-jquery", "chai-jquery"],
+        ["cross-browser", "cross browser"],
         ["cross origin", "cross-origin"],
         "ESLint",
         ["Express.js", "Express"],