Init mixpanel and amplitude analytics

[sl1depengwyn]

Closes #6347

Docs update blockscout/docs#96

Changelog

Added following analytics events:

• Profile button click either in account page menu or in navbar account dropdown event name: 'Profile click'
• Watch list button click either in account page menu or in navbar account dropdown event name: 'Watch list click'
• Address tags button click either in account page menu or in navbar account dropdown event name: 'Address tags click'
• Transaction button click either in account page menu or in navbar account dropdown event name: 'Transaction tags click'
• API keys button click either in account page menu or in navbar account dropdown event name: 'API keys click'
• Custom ABI button click either in account page menu or in navbar account dropdown event name: 'Custom ABI click'
• Public tags button click either in account page menu or in navbar account dropdown event name: 'Public tags click'
• Sign out button click in navbar account dropdown event name: 'Sign out click'
• Sign in button click in navbar event name: 'Sign in click'
• Add address to watch list button click in account watch list page event name: 'Add address to watch list click'
• Add address tag button click in account address tags page event name: 'Add address tag click'
• Add transaction tag button click in account transaction tags page event name: 'Add transaction tag click'
• Add API key button click in account API keys page event name: 'Add API key click'
• Add custom ABI button click in account custom ABI page event name: 'Add custom ABI click'
• Request to add public tag click in account public tags page event name: 'Request to add public tag click'
• Add address to watch list

event name: 'New address to watchlist completed', 
event properties: {
    address_hash: string,
    private_tag: string,
    eth_incoming: bool,
    eth_outgoing: bool,
    erc_20_incoming: bool,
    erc_20_outgoing: bool,
    erc_721_1155_incoming: bool,
    erc_721_1155_outgoing: bool,
    email_notifications: bool
}

• Add address tag

event name: 'Add address tag completed', 
event properties: {
    address_hash: string,
    private_tag: string
}

• Add transaction tag

event name: 'Add transaction tag completed',
event properties: {
    address_hash: string,
    private_tag: string
}

• Add API key

event name: 'Generate API key completed',
event properties: {
    application_name: string
}

• Add custom ABI

event name: 'Custom ABI completed',
event properties: {
    smart_contract_address: string,
    project_name: string,
    custom_abi: string
}

• Send public tag request

event name: 'Request a public tag completed',
event properties: {
    name: string,
    email: string,
    company_name: string,
    company_website: string,
    goal: 'Add tags' or 'Incorrect public tag',
    public_tag: string,
    smart_contracts: list of strings,
    reason: string
}

• Searching at the nav bar

event name: 'Occurs searching according to substring at the nav bar',
event properties: {
    search: string
}

• Search results displays at the nav bar

event name: 'Search list displays at the nav bar',
event properties: {
    resultsNumber: int,
    results: list of strings
}

• User clicks search result at the nav bar

event name: 'Search item click at the nav bar',
event properties: {
    item: string
}

• Searching at the search page

event name: 'Occurs searching according to substring at the search page',
event properties: {
    search: string
}

• Search results displays at the search page

event name: 'Search list displays at the search page',
event properties: {
    resultsNumber: int,
    results: list of strings
}

• User clicks search result at the search page

event name: 'Search item click at the search page',
event properties: {
    item: string
}

Checklist for your Pull Request (PR)

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so by submitting a PR to https://github.com/blockscout/docs
• If I added/changed/removed ENV var, I submitted a PR to https://github.com/blockscout/docs to update the list of env vars at https://github.com/blockscout/docs/blob/master/for-developers/information-and-settings/env-variables.md and I updated the version to master in the Version column. Changes will be reflected in this table: https://docs.blockscout.com/for-developers/information-and-settings/env-variables. (Add envs for analytics integration docs#96)
• If I add new indices into DB, I checked, that they are not redundant with PGHero or other tools

[vbaranov]

@sl1depengwyn please rebase

[sl1depengwyn]

@sl1depengwyn please rebase

Done

[vbaranov]

@sl1depengwyn please add introduced env vars into docker-compose env vars and into Makefile and Dockerfile.