hotkey.js: Navigate using page up / page down
hotkey.js: Navigate using page up / page down

Using page up / page down, go to the top / bottom of compose textarea

Fixes https://github.com/zulip/zulip/issues/7097

shubhamdhama/zulip,andersk/zulip,punchagan/zulip,brainwane/zulip,eeshangarg/zulip,mahim97/zulip,showell/zulip,synicalsyntax/zulip,rht/zulip,dhcrzf/zulip,timabbott/zulip,tommyip/zulip,hackerkid/zulip,shubhamdhama/zulip,punchagan/zulip,eeshangarg/zulip,synicalsyntax/zulip,jackrzhang/zulip,timabbott/zulip,brainwane/zulip,eeshangarg/zulip,dhcrzf/zulip,brainwane/zulip,timabbott/zulip,andersk/zulip,showell/zulip,tommyip/zulip,punchagan/zulip,synicalsyntax/zulip,dhcrzf/zulip,mahim97/zulip,tommyip/zulip,punchagan/zulip,mahim97/zulip,rishig/zulip,kou/zulip,zulip/zulip,rht/zulip,zulip/zulip,andersk/zulip,dhcrzf/zulip,rishig/zulip,dhcrzf/zulip,synicalsyntax/zulip,mahim97/zulip,mahim97/zulip,punchagan/zulip,shubhamdhama/zulip,hackerkid/zulip,showell/zulip,kou/zulip,shubhamdhama/zulip,brainwane/zulip,timabbott/zulip,zulip/zulip,jackrzhang/zulip,zulip/zulip,rishig/zulip,rht/zulip,jackrzhang/zulip,kou/zulip,dhcrzf/zulip,hackerkid/zulip,jackrzhang/zulip,andersk/zulip,tommyip/zulip,rht/zulip,timabbott/zulip,shubhamdhama/zulip,synicalsyntax/zulip,rht/zulip,hackerkid/zulip,eeshangarg/zulip,timabbott/zulip,shubhamdhama/zulip,shubhamdhama/zulip,zulip/zulip,eeshangarg/zulip,andersk/zulip,timabbott/zulip,andersk/zulip,tommyip/zulip,jackrzhang/zulip,rishig/zulip,punchagan/zulip,kou/zulip,tommyip/zulip,zulip/zulip,synicalsyntax/zulip,hackerkid/zulip,synicalsyntax/zulip,kou/zulip,brainwane/zulip,dhcrzf/zulip,hackerkid/zulip,showell/zulip,kou/zulip,hackerkid/zulip,tommyip/zulip,jackrzhang/zulip,jackrzhang/zulip,showell/zulip,andersk/zulip,kou/zulip,rishig/zulip,brainwane/zulip,showell/zulip,eeshangarg/zulip,mahim97/zulip,brainwane/zulip,rishig/zulip,showell/zulip,rht/zulip,eeshangarg/zulip,punchagan/zulip,rishig/zulip,rht/zulip,zulip/zulip