add support for XL-MaxSonar-WR/WRC MaxBotix sensors

Hello Community =)

**Describe the problem you have/What new integration you would like**

ESPHome already supports the high resolution (hr) versions of the maxbotix distance sensors, but it would be nice to also support other models. Specifically, the XL-MaxSonar-WR series with model numbers MB70XX and MB71XX as given in this datasheet: https://www.maxbotix.com/documents/XL-MaxSonar-WR_Datasheet.pdf

**Please describe your use case for this integration and alternatives you've tried:**

Got my hands on a MB7052 and using a MAX232 converter to convert RS232 to TTL. It all works, the esp8266 receives bytes without a problem, but the provided sensor platform for hrxl_maxsonar_wr will only log "Invalid data read from sensor: %s"

I found a workaround using a text sensor to read the bytes and convert them to int in HA downstream, but this solution lacks nice features like filters and throttling (which are very much desired at a publishing frequency of 6.6 Hz).

**Additional context**

Looking at the source code, I found that the control flow requires a buffer length of 6 for values to get published. However, the lower precision versions will only send bytes with a total length of 5, e.g. 'R012\r' and not 'R0123\r'. As a result, the values are never published because the if condition never evaluates to true.

I tried to tweak the hrxl_maxbotix_wr.cpp file, but couldn't find it. Simply replacing the value in line 17 would suffice, I guess.
`static const int MAX_DATA_LENGTH_BYTES = 5; // priviously 6`
Since this would also help my situation, I'd be grateful for advice on how to locate esphome source files in my HA installation.

Start with hrxl_maxbotix_wr.cpp and inspect the data-length check mentioned in the issue. Verify the MB7052's five-byte readings are accepted and published, then check that filters and throttling still work at the requested frequency; the issue does not name a test file.

Written by the indexing model from the issue text.