Update alts and headings

[avivash]

Description

• Add more context to alt tags(e.g. Laconic -> Laconic logo)
• Add h1 with the word Fission in it and the sr-only class
• Bump all headings down by 1(e.g. h2->h3), but retain styles
• Officially add a PR template to the app so I don't have to copy and paste it each time 😅

Note: This PR doesn't address any colour/readability issues mentioned in the thread because I think we'll have a design session to figure out the best way to address those discrepancies

PR Preview

https://tubular-triangular-yellow-cat.fission.app/

Link to issue

https://discord.com/channels/478735028319158273/766358587752316998/964385816019341362

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)

Screenshots/Screencaps

An updated alt attribute:

[avivash]

@depatchedmode i noticed the hyperlinks in the project blocks are purple for both the light and dark modes. was that intentional or do you want me to make them yellow for dark mode to match the figma file?

[avivash]

@chadkoh i added a hidden h1 for screen readers only that has the word Fission in it. The text following Fission is the same as the h2 that comes after it though. Do you think I should update the h1 to say something else?

<h1 class="sr-only">Fission: Building protocols for the future of the internet</h1>

[avivash]

@depatchedmode @chadkoh i'll probably just merge this unless you have any objections?