Careers page update [L]

[ukorvl]

• Use freshteam api to load positions list for https://nil.foundation/careers/jobs and concrete position for each position page
• Use SSG because all positions info can be fetched on backend and static pages can be generated.
• Create urls to exact positions and support old urls, which are already posted on a lot of sources, urls should be the same https://nil.foundation/careers/jobs?jobId=IpNIuwrbvK2s
• Implement positions filtering and searching by text

On freshteam side:

Use code editor to insert headings and make all pages look the same.

[ukorvl]

Done.