Bump ESPAsyncWebServer-esphome to v1.2.7

[OttoWinter]

Description:

Includes esphome/ESPAsyncWebServer#1 :

• Fixes AsyncEventSource::send()
• Increases SEE_MAX_QUEUED_MESSAGES to 32 on ESP8266.

Status: Waiting for platformio lib crawler to pick up the change. See https://platformio.org/lib/show/6758/ESPAsyncWebServer-esphome

Related issue (if applicable): fixes esphome/issues#806

Checklist:

• The code change is tested and works locally.
• [N/A] Tests have been added to verify that the new code works (under tests/ folder).

[OttoWinter]

Tested with:

.test: &test
  platform: template
  lambda: 'return {"Hello World!"};'

web_server:

text_sensor:
  - <<: *test
    name: Text Sensor 1
  - <<: *test
    name: Text Sensor 2
  - <<: *test
    name: Text Sensor 3
  - <<: *test
    name: Text Sensor 4
  - <<: *test
    name: Text Sensor 5
  - <<: *test
    name: Text Sensor 6
  - <<: *test
    name: Text Sensor 7
  - <<: *test
    name: Text Sensor 8
  - <<: *test
    name: Text Sensor 9
  - <<: *test
    name: Text Sensor 10
  - <<: *test
    name: Text Sensor 11

Result: all 11 text sensors appear on the web server frontend.

[rradar]

Works as expected now 🎉

Thank's for this 🍒