Feat: Add status page countdown to refresh

[chakflying]

⚠️⚠️⚠️ Since we do not accept all types of pull requests and do not want to waste your time. Please be sure that you have read pull request rules:
https://github.com/louislam/uptime-kuma/blob/master/CONTRIBUTING.md#can-i-create-a-pull-request-for-uptime-kuma

Tick the checkbox if you understand [x]:

• I have read and understand the pull request rules.

Description

Partially addresses #978. Refresh interval not configurable yet, but value is stored in vue.js data now instead of hard-coded.

Type of change

Please delete any options that are not relevant.

• User interface (UI)

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• I have commented my code, particularly in hard-to-understand areas
  (including JSDoc for methods)
• My changes generate no new warnings
• My code needed automated testing. I have added them (this is optional task)

Screenshots (if any)

[JacksonTheMaster]

@louislam @chakflying i may be stupid but how on earth do I edit the value? I'm using the docker container, thought of just editing it in the bind mounted files but I cant find StatusPage.vue anywhere in the container..Im not a developer, probably im missing some basic stuff....Thx in advance :*

[chakflying]

I'd say currently manually editing the value is not feasible unless you are experienced with JavaScript.

[JacksonTheMaster]

Thx for the clarification! JavaScript & specifically vue.js sadly is not my cup of tea :)