Add read-only permission for organizations and dynamic token check at current block

[jjranalli]

Read Only

When giving access to repos owned by an organisation, new members get "write" access by default. This may be undesirable.

• Added read-only option during gate creation (only shows up if repo is owned by an org)
• Added readOnly to Gate in db schema
• Added frontend elements related to read-only option
• Changed .env.sample and readme
• Fixed links that were hardcoded to 'gaterepo.com'

Dynamic Check

Checking number of tokens held dynamically and not at a specific block might be desirable in some scenarios. For example, it avoids having to periodically create new links to allow new holders to get access to the repo.

• Added Dynamic check option during gate creation
• Added required logic in api/gates endpoints
• Added dynamicCheck to Gate in db schema + added default values to both dynamicCheck and readOnly proposed in Add read-only option for organization-owned repos #3 (should prevent issues during db migration)
• Added frontend elements related to dynamic check option

Btw great work doing this ❤️