Add avatar max size limit

.../account/account-settings/account-settings.component.html

.../account/account-settings/account-settings.component.scss

...pp/account/account-settings/account-settings.component.ts

client/src/app/core/server/server.service.ts

package.json

server.ts

server/controllers/api/config.ts

server/helpers/custom-validators/activitypub/actor.ts

server/helpers/custom-validators/activitypub/misc.ts

server/initializers/constants.ts

server/middlewares/validators/users.ts

server/models/activitypub/actor.ts

server/models/server/server.ts

server/tests/api/check-params/users.ts

server/tests/api/fixtures/avatar-big.png

shared/models/server-config.model.ts

yarn.lock