docs: Add debugging tip for failure when typing on modal with puppeteer.
docs: Add debugging tip for failure when typing on modal with puppeteer.

punchagan/zulip,eeshangarg/zulip,hackerkid/zulip,zulip/zulip,andersk/zulip,andersk/zulip,hackerkid/zulip,kou/zulip,punchagan/zulip,zulip/zulip,andersk/zulip,rht/zulip,andersk/zulip,hackerkid/zulip,andersk/zulip,eeshangarg/zulip,eeshangarg/zulip,kou/zulip,zulip/zulip,rht/zulip,rht/zulip,hackerkid/zulip,rht/zulip,hackerkid/zulip,rht/zulip,zulip/zulip,rht/zulip,andersk/zulip,rht/zulip,zulip/zulip,kou/zulip,zulip/zulip,andersk/zulip,eeshangarg/zulip,punchagan/zulip,eeshangarg/zulip,zulip/zulip,punchagan/zulip,kou/zulip,kou/zulip,punchagan/zulip,eeshangarg/zulip,kou/zulip,eeshangarg/zulip,punchagan/zulip,punchagan/zulip,hackerkid/zulip,kou/zulip,hackerkid/zulip