Create function include_diabetes_diagnosis()

[signekb]

Following the functionality flow, this function filters necessary diagnoses from lpr_adm and lpr_diag to create the diabetes cohort.

osdc/vignettes/function-flow.Rmd

Lines 85 to 98 in 375e652

	### Hospital diagnosis of diabetes
	The function `include_diabetes_diagnoses()` uses the hospital contacts
	from LPR2 and 3 to include all dates of diabetes diagnoses. Diabetes
	diagnoses from both ICD 8 and ICD 10 are included.
	This function contains two helper functions:
	- `keep_diabetes_icd10()`
	- `keep_diabetes_icd8()`
	<!-- TODO: Add details on how this filtering should be done, e.g., diagnosis codes -->
	<!-- TODO: Which specific ICD 8 and 10 codes are included? -->

From @Aastedet 's original issue #6 :

At a point we may have to address differences between LPR2 and LPR3 data, unless we delegate that to the users' preprocessing of raw data.

[lwjohnst86]

Include logic in algorithm.csv as well