Add id in the contribute page so we can directly link to them

[karlcow]

1. Someone is asking on how to execute a specific task for contributing to webcompat
2. Going to the contribute page
3. Clicking on the section, there is no permalink,

Consequence: We can't share easily the information in a specific section

Suggestion:

• Add ids on h2 elements
• Add anchors #id when clicking on a section.