feat: ETC support and notifications tests

- Add ETC to the list of supported coins. A new `coin` setting can be
  configured to avoid conflict with `eth`. Mind the lowercase. By default,
  flexassitant will try to deduce the coin from the miner's address (with eth by
  default, not etc). (#5)

- Add `test` (true/false) to `notifications` section to test notifications with
  random values fetched from the Flexpool API

- Fix typo in the configuration example (#6)

BREAKING CHANGE: `notification-templates` configuration settings have been
renamed to `notifications`, with sections to configure balance, payment, block
and offline workers notifications, with `template` and `test` settings.

Signed-off-by: Julien Riou <julien@riou.xyz>

flexassistant.example.yaml

@@ -0,0 +1,39 @@
+---
+database-file: flexassistant.db
+max-blocks: 10
+max-payments: 5
+miners:
+  - address: 0x0000000000000000000000000000000000000000
+    coin: eth
+    enable-balance: true
+    enable-payments: true
+    enable-offline-workers: true
+  - address: xch00000000000000000000000000000000000000000000000000000000000
+    coin: xch
+    enable-balance: true
+    enable-payments: true
+    enable-offline-workers: true
+pools:
+  - coin: eth
+    enable-blocks: true
+    min-block-reward: 10
+  - coin: xch
+    enable-blocks: true
+    min-block-reward: 1.79
+telegram:
+  chat-id: 000000000
+  channel-name: MyTelegramChannel
+  token: 0000000000000000000000000000000000000000000000
+#notifications:
+#  balance:
+#    template: balance.tmpl
+#    test: true
+#  block:
+#    template: block.tmpl
+#    test: true
+#  offline-worker:
+#    template: offline-worker.tmpl
+#    test: true
+#  payment:
+#    template: payment.tmpl
+#    test: true